Homemade rainbow cake made with layers of moist vanilla buttermilk cake and easy buttercream frosting
This rainbow cake just makes me feel so happy. I absolutely LOVED slicing into it to see all those gorgeous colorful layers! The best part is, this rainbow cake isn't just for looks, it tastes absolutely amazing. You won't have a crumb leftover.
This rainbow cake is very special to me. I've been waiting to make it for a long time. Ever since we found out we were pregnant with our son, Ezra, I knew I wanted to make him a rainbow cake for his half birthday (6 months).
Most people know that my husband and I had to go through a lot of infertility treatments to get our dear Avalon. I'm not ashamed of it. I think we should talk more about infertility and how common it is. So we feel less alone.
We started treatments TWO years ago. Nothing was working. My body was fighting against me. I was not in a good place emotionally or mentally.
It might sound crazy but I had a dream we had a son. I didn't tell anyone but I held onto hope as best I could.
We had honestly almost given up that we would ever have a second child. But I just felt in my soul that we had a second child waiting for us. So we didn't give up.
After all those treatments and all those medications, we ended up with ONE single egg. If you've gone through IVF you. know that the chances of that ONE egg taking are extremely low. I did not get my hopes up.
But that one egg did stick. And here we are with our beautiful baby boy. Our rainbow after the storm. Our lucky charm. The completion of our family.
What cake recipe is best for rainbow cake?
So the first thing that we have to do is bake our rainbow layers. This might sound intimidating but it's actually really easy.
We're going to use my favorite cake, white velvet. Not only. is this cake delicious, but it's also very white so it will take the color well.
If you try to add color to a vanilla cake that has egg yolks in it, those yolks will distort your colors while baking.
The other reason white velvet is perfect for making a rainbow cake is that it won't get over-mixed when you add the color.
I've added color to white velvet so many times, making everything from pink velvet, green velvet, and even blue velvet. The texture always turns out amazing.
How to make rainbow cake layers
Get your 8"x2" cake pans ready. You might not have 6 cake pans all the same size (I don't) so keep your cake batter in the fridge while your other cakes are baking. They are really thin so they bake up fast.
Coat your cake pan in a layer of cake goop and preheat your oven to 335ºF. I also put a piece of parchment paper in the bottom of my pans so that they were easier to take out of the pan since they would be so thin.
To make our rainbow cake layers, all you have to do is mix up your batter (follow the recipe below) and then divide your batter into 6 bowls evenly.
Each bowl holds 15 ounces of cake batter. I used a kitchen scale to weigh mine out so they would all be equal.
I'm using electric colors from Americolor and I'm not making an EXACT rainbow, this rainbow is more Lisa Frank style. I really like these electric colors because they make super bright neon colors and you don't have to use a lot of food color.
Colors I used
- Electric Purple
- Electric Blue
- Electric Green
- Electric Yellow
- Electric Orange
- Electric Pink
You can totally go classic rainbow and use red instead of pink, violet instead of electric purple and royal blue instead of electric blue.
Add a drop or two of color to each bowl and stir with a spoon until combined. Make sure for the green you use a little yellow and a little green so the green is more vibrant.
For the orange, use a little orange and a little yellow to make the orange more vibrant.
For the purple, add a little pink and purple to make the purple more vibrant.
Pour your batter into your cake pans (I baked three at a time and put 15 ounces of batter in each pan).
When they are done baking, they will start to pull a tiny bit from the edges of the pan (that's normal) let them cool a bit in the pan before turning out onto a cooling rack to fully cool down.
I put my cakes into the freezer for about 30 minutes to firm them up before trimming off the dome, the brown sides, and the brown bottom.
Trimming your cakes just makes the slices extra perfect and beautiful when you slice them.
How to decorate a rainbow cake
Time to decorate our rainbow cake! I'm using my easy buttercream because it comes together so fast. You could use any buttercream though like swiss meringue buttercream, Italian meringue buttercream or even cream cheese frosting.
Place your first layer onto your cake board. I'm working on a turntable to make this whole process easier.
Apply a thin layer of buttercream. Shoot for about ¼" of frosting.
Keep your spatula nice and flat so your buttercream has an even thickness.
I'm starting with the purple because that makes sense to me in my brain but you could start with the pink if you want to go in the opposite direction.
Continue frosting and stacking this way with the rest of the layers and then give the whole cake a nice crumb coat to seal in all those rainbow crumbs.
Chill your cake for 15 minutes to firm up that layer of buttercream.
Finish your cake with a final layer of buttercream and smooth it out with your bench scraper and offset spatula.
After chilling my cake, I added some fancy sprinkles to the bottom border of the cake, then I transferred my cake to a cake board.
I'm finishing this cake with a water ganache drip. I used 5 ounces of white candy melts, 1 ounce of chocolate candy melts and 6 ounces of water.
After melting, I added a few drops of electric yellow food coloring to make a gold candy melt color. I dripped this water ganache onto my chilled cake. Then painted gold with some truly mad plastics gold dust and vodka.
Make sure your mixture of dust and vodka is fairly thick, like paint so that you get good coverage.
Then I added some little swirls of white frosting on top and added some more sprinkles. I used a 1M piping tip to do the swirls.
And we're done with our rainbow cake! Doesn't it look so pretty! I love how the slices look and they are the perfect accent to this month's Ezra photo.
Cake Batter and Frosting Calculator
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Cups of Batter Needed
8 cups
Cups of Frosting Needed
5 cups
Note: measurements are estimated based off the vanilla cake recipe using standard US cake pans and sizes. Measurements used are for 2" tall cake pans only. Your results may vary. Do not overfill cake pans above manufacturer's recommended guidelines.
Recipe
Equipment
- Stand Mixer
- Whisk Attachment
- Paddle Attachment
- Turntable
- Offset Spatula
- Piping Bag
- 1M Piping Tip
Ingredients
Rainbow Cake Ingredients
- 24 oz cake flour
- 24 oz granulated sugar
- 1 teaspoon salt
- 2 tablespoon baking powder
- 1 teaspoon baking soda
- 10 oz egg whites room temperature
- 6 oz vegetable oil
- 18 oz buttermilk room temperature or slightly warm
- 12 oz butter unsalted and softened
- 1 Tablespoon vanilla extract
Easy Buttercream Frosting Ingredients
- 8 oz pasteurized egg whites
- 32 oz powdered sugar
- 32 oz unsalted butter softened but not melted
- 2 teaspoon vanilla extract
- ½ teaspoon salt
- 1 dot purple food coloring to make the buttercream white
Gold Drip
- 5 oz white candy melts
- 1 oz chocolate candy melts
- 1 oz hot water
- 1 teaspoon Truly mad plastics super gold dust
- ¼ teaspoon everclear or vodka or lemon extract
Instructions
- NOTE: It is SUPER IMPORTANT that all the room temperature ingredients listed above are room temperature and measured by weight so that the ingredients mix and incorporate correctly. Heat oven to 335º F/168º C
- Prepare six ( 8"x2") cake pans with cake goop and place a round piece of parchment paper in the bottom of the pan for easy removal of the cake
- Combine 8 oz of the buttermilk and the oil together and set aside.
- Combine the remaining buttermilk, egg whites, and vanilla together, whisk to break up the eggs and set aside.
- Combine flour, sugar, baking powder, baking soda and salt in the bowl of a stand mixer with the paddle attachment. Mix 10 seconds to combine.
- Add your softened butter to the dry ingredients and mix on low until mixture resembles coarse sand (about 30 seconds).
- Add in your milk/oil mixture and let mix until dry ingredients are moistened and then bump up to med (setting 4 on my KitchenAid) and let mix for 2 full minutes to develop the cake's structure. If you don't let your cake mix on this step your cake could collapse.
- Scrape your bowl and then reduce speed to low. Add in your egg white/milk mixture in three batches, letting the batter mix for 15 seconds between additions. Scrape down the sides again to make sure everything has incorporated.
- Divide your batter into 6 bowls. Weigh 15 ounces of batter for each bowl.
- Color each bowl with your Electric food colors. ½ teaspoon for pink for the pink layer, ¼ teaspoon yellow plus ¼ teaspoon orange for orange layer, ½ teaspoon yellow for yellow layer, ¼ teaspoon yellow plus ½ teaspoon green for green layer, ½ teaspoon blue for blue layer, ¼ teaspoon pink and ½ teaspoon purple for the purple layer.
- Bake your layers for 20-24 minutes or until the edges JUST start pulling away from the cake pan. Do not under-bake or the middle of the cake will collapse.
- IMMEDIATELY TAP PAN FIRMLY on countertop once to release the steam from the cake. This stops the cake from shrinking.
- Let cakes cool for 10 minutes inside the pan before flipping them out. The cake will shrink a bit and that is normal. Freeze your cake layers 30-60 minutes before trimming your cakes. Frost and fill with buttercream frosting.
- After your buttercream is smooth, place the cake back into the fridge for 15 minutes before you apply your drip.
- Wait for your drip to set before painting with gold paint. Finish the cake with buttercream rosettes and more sprinkles.
Easy Buttercream Instructions
- Place powdered sugar and pasteurized egg whites in the bowl of your stand mixer with the whisk attachment.
- Mix on low to combine then increase speed to high.
- Add the butter in small chunks while mixing. Continue mixing until all the butter is added in. Then add in your vanilla and salt.
- Mix on high until light and fluffy and no longer tastes like butter. Add a dot of purple food coloring to reduce the yellow appearance of the buttercream (optional).
- Remove the whisk attachment and replace it with the paddle attachment. Mix on low for 10 minutes to remove bubbles from the buttercream.
Gold Drip Instructions
- Melt the chocolate in the microwave in 15-second increments until almost fully melted.
- Add in your hot water and microwave another 15 seconds
- Stir until smooth. Then add in your yellow food coloring. Stir until smooth.
- Place water ganache into a piping bag, snip off the tip and drip the ganache around the edge of your chilled cake. After it sets, you can mix your gold dust and vodka together and paint the drip gold
Video
Notes
Cake flour sources: UK - Shipton Mills Cake & Pastry Flour
Natalia Pena says
Beautiful !!!!!! Congratulations again . I have a question . I love using some kind of fruit flavors for filling between layers . You think this will ruin the look of this cake ? Or can I made strawberry butter cream for the inside ?
Thanks!!!
Elizabeth Marek says
If the fruit filling is very thin, I think it would be ok 🙂
Tahnee says
Hi Liz,
I'm planning to make this for my daughter's birthday. If I make it the night before will that be ok? Also will I have to refrigerate it?
Elizabeth Marek says
Yes you can definitely make it the day before, I do keep mine in the refrigerator but take them the morning of the event so that the cakes have time to warm up
Leigh says
Thanks for the great recipe and thorough instructions. I made this for my daughter's 2nd birthday. I used less intense colours for a more pastel look. I'm pregnant and wasn't sure about having buttercream with uncooked egg white, so I used your crusting cream cheese frosting instead, flavoured with lemon extract and a bit of zest. Delicious! I also did just plain dark chocolate ganache for the drip, rather than gold.
Elizabeth Marek says
Yay! I'm so glad! Just fyi for the future, pasteurized egg whites are heat treated the same way that milk is so they are perfectly fine to eat 🙂
Pontsho Modiba says
I loved the recipe so much. I haven't really found one that works for me. What will happen if I add whole eggs and not whites only?
Elizabeth Marek says
The egg yolks will affect the colors of the cake
Katherine says
Hi there!
I'm wondering if you used liquid food colouring or gel? Does it matter?
Thanks!!
Elizabeth Marek says
I used gel, I think you could use liquid too
Victoria Richmond says
This is the best cake i have EVER made, it looks so so good and tastes amazing. Everyone was so impressed with it. It was worth the effort and cutting the brown off made it perfect for presentation. I was asked by multiple people about where the cake came from.
Catherine says
Hi
I’m in Australia and would love to make the rainbow cake for my little boy’s 4th birthday. I just have a few questions in regards to the sugar. Is granulated sugar the same as caster sugar and is powdered sugar the same as icing sugar or is it icing mixture which has cornflour in it ? Also I have bought the americolor food colouring in the gel paste form. Is your recipe based using the gel paste food colouring or is it the air brush food colouring which I assume is liquid based? Your help would be greatly appreciated.
Elizabeth Marek says
Granulated and caster are pretty much the same, as well as powdered and icing sugar. I am using gel colors.
Diana says
This cake is DELICIOUS! You have inspired me so much! I made my daughter's 2nd Birthday cake using this recipe, your buttercream, and fodant recipe. I made her an "Abby Sesame Street" cake and it came out beautiful and delicious. Seriously. I want cake now.
Tashi says
Hi Liz,
I want to make this for a unicorn party my family is having. I was wondering if I can do a 6in cake with this and if so how much batter should I put in the pan. I don't want to screw this up lol
Elizabeth Marek says
I would suggest not using anything smaller than the 8" or your cake will be too tall and skinny and might fall over
Lauren says
I am mesmerized by your final product and hope to reproduce your perfect cake this weekend for my daughters birthday. It will be a surprise so I will be doing it at night after the kids are asleep. Due to this, I want to try and spread it out over two nights. I have a couple questions about that
1. Does the cake need to cool completely before placing the layers in the fridge?
2. How do I store the layers in the fridge? Wrapped individually in plastic wrap?
Thank you so much!
Elizabeth Marek says
They can be a little warm before wrapping them in plastic wrap to cool in the fridge
Arlene Hernandez says
You’re precise directions were easy to follow! I made two of these beautiful cakes for my 6 year old twin nieces. Now wish me luck on the cutting. Thank you for sharing, because of you my cakes will be the talk of the town !
Chantelle Lotter says
Tried this recipe this past weekend. Absolutely amazing, delicious!! My cakes didn't rise very much, baked cakes were just short of an inch high, is this correct?
Still resulted in high cake due to all the layers.
Elizabeth Marek says
Yes they are short because there are 6 layers!
Catherine says
Thank you so much for getting back to me.
I’ll let you know how it goes.
Catherine
Lois says
Very excited to make this cake for my daughter! Will 9” cake pans work? Or should I increase the batter?
Elizabeth Marek says
You don't need to increase the batter for a 9" pan
Nat says
Hi Liz
I messaged a few days ago, not sure if it actually went through.
We don’t have cake flour where I am. Would you be able to recommend a substitution for it or perhaps suggest another one of your recipes that I could use for the rainbow cake?
Thank you.
Elizabeth Marek says
You can use the white cake recipe instead if you can't find cake flour 🙂
Zarina Buzadzhi says
How many layers does one batch make?
Elizabeth Marek says
The recipe is enough batter for all the layers.
Malini Kothapalli says
I made the cake for my daughter's 10th birthday. Loved every bit of it.
Anne-Sophie says
I am going to try this cake for my daughter's birthday, Will it work if I had cocoa powder to the buttercream? She wanted a chocolate icing rainbow cake !! thank you
Elizabeth Marek says
If you add cocoa powder it will make the colors brown
Meenam Moodley says
Hii, I just want to know how necessary it is to use pasteurized egg whites and how it affects the recipe as compared to using normal egg whites. i couldn't find pasteurized egg whites in the store, neither do I have a thermometer to accurately pasteurize them myself. I've cooked with normal egg whites before so if the sole purpose of pasteurized eggs is to be heat treated can I just use normal ones instead?
Thank you.
Elizabeth Marek says
Pasteurized egg whites are already heat treated so they are safe to eat when you aren't cooking them. If you used regular egg whites they would not be safe to eat. You can either use the swiss meringue buttercream recipe instead or you can read my how to pasteurize your own eggs blog post
Thekla Charalambous says
Hi from the uk.
I’m so inspired to give this a go.
Do you use a fan assisted oven.
Thank you
Elizabeth Marek says
I use a conventional oven
Pia says
Thank you so much for sharing this great recipe! I watched the video multiple times and the cake turned out perfect for my son's 5th birthday even though I had never tried to make a cake like this before. Your tips are amazing!
Katrina Walker Hair says
I made this cake for my daughters’ 13th birthday and she LOVED IT! The best cake she’d ever had was her exact words. Thank you!!!!
Chelsea says
I want to make this cake tomorrow for my sons birthday, but I only have a hand mixer with the standard whisk attachments. Will that be a problem since I don’t have a paddle mixer?
Elizabeth Marek says
Hand mixer will work just fine
Tanya Speer says
This cake is delicious and beautiful! The colors were so vibrant. I actually made the cake layers and frosted with a different chocolate buttercream (added black food coloring to make the colors pop). It was great! Thank you for a great cake.
Lori says
Congratulations on baby!! How exciting!! I made your WASC cake for my son's 1st back in March and I'm planning on making this rainbow cake, with the WASC for my little girls 7th bday. She asked for a rainbow cake, but just like brothers. Looking forward to it!! Any modifications needed with using WASC recipe and gel coloring?
Elizabeth Marek says
No modifications! Try not to fill your pans too much or the layers get really tall 😀 Have fun!