Rainbow Cake

Not only is this rainbow cake beautiful and colorful, but it also tastes really delicious. Made from my famous white velvet cake recipe and easy buttercream, this rainbow cake makes the perfect special occasion cake!
*note* if you adjust the cake pan size using the calculator, keep in mind that the pans should only be filled halfway (1" tall) so the layers are not too big. The calculator is formulated for 2" tall layers.
↓ Recipe ↓ Video Print Recipe
Total Time: 40 mins
Serves: 14 cups
slice of rainbow cake on blue plate white background and whole cake in background

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. 

slice of rainbow cake on blue plate white background and whole cake in background

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.

closeup of buttercream frosting on gold drip cake with rainbow sprinkles

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. 

6 month old baby boy on white background with rainbow cake slices around him

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.

white velvet cake withe ermine frosting

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. 

8" cake pan with parchment paper and cake goop

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. 

6 bowls of white velvet cake ready to be colored

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

  1. Electric Purple
  2. Electric Blue
  3. Electric Green
  4. Electric Yellow
  5. Electric Orange
  6. Electric Pink

americolor electric colors

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. 

6 bowls of white velvet cake all colored rainbow

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.

rainbow cakes finished baking and cooling on racks 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. 

layers of rainbow cake stacked on top of each other

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 1/4″ 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. 

layers of rainbow cake with buttercream frosting in between

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. 

rainbow cake with layer of frosting for the crumb coat

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. 

rainbow cake with smooth layer of buttercream frosting

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.

making water ganache

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. 

rainbow cake with gold drip and rainbow sprinkles

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. 

slice of rainbow cake on blue plate and gold fork

Cake Batter and Frosting Calculator

Select an option below to calculate how much batter or frosting you need. Adjust the servings slider on the recipe card to change the amounts the recipe makes.

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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.

Did You Make This Recipe?Leave a rating and tell me how it went!
slice of rainbow cake on blue plate white background and whole cake in background

Rainbow Cake

Not only is this rainbow cake beautiful and colorful, but it also tastes really delicious. Made from my famous white velvet cake recipe and easy buttercream, this rainbow cake makes the perfect special occasion cake!
*note* if you adjust the cake pan size using the calculator, keep in mind that the pans should only be filled halfway (1" tall) so the layers are not too big. The calculator is formulated for 2" tall layers.
5 from 155 votes
Print Rate
Prep Time: 20 mins
Cook Time: 20 mins
Total Time: 40 mins
Serves: 14 cups
Calories: 853kcal

Ingredients

Rainbow Cake Ingredients

  • 24 oz (680 g) cake flour
  • 24 oz (680 g) granulated sugar
  • 1 tsp (1 tsp) salt
  • 2 Tbsp (2 Tbsp) baking powder
  • 1 tsp (1 tsp) baking soda
  • 10 oz (283 g) egg whites room temperature
  • 6 oz (170 g) vegetable oil
  • 18 oz (510 g) buttermilk room temperature or slightly warm
  • 12 oz (340 g) butter unsalted and softened
  • 1 Tablespoon (1 Tablespoon) vanilla extract

Easy Buttercream Frosting Ingredients

  • 8 oz (227 g) pasteurized egg whites
  • 32 oz (907 g) powdered sugar
  • 32 oz (907 g) unsalted butter softened but not melted
  • 2 tsp vanilla extract
  • 1/2 tsp (1/2 tsp) salt
  • 1 dot (1 dot) purple food coloring to make the buttercream white

Gold Drip

  • 5 oz (142 g) white candy melts
  • 1 oz (28 g) chocolate candy melts
  • 1 oz (170 g) hot water
  • 1 tsp Truly mad plastics super gold dust
  • 1/4 tsp everclear or vodka or lemon extract

Equipment

  • Stand Mixer
  • Whisk Attachment
  • Paddle Attachment
  • Turntable
  • Offset Spatula
  • Bench scraper
  • Piping Bag
  • 1M Piping Tip

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. 1/2 tsp for pink for the pink layer, 1/4 tsp yellow plus 1/4 tsp orange for orange layer, 1/2 tsp yellow for yellow layer, 1/4 tsp yellow plus 1/2 tsp green for green layer, 1/2 tsp blue for blue layer, 1/4 tsp pink and 1/2 tsp 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

Notes

This cake is very TALL (about 7") so your slices will be very tall. You could cut them in half but then you'd ruin the rainbow. 
*note* if you adjust the cake pan size using the calculator, keep in mind that the pans should only be filled halfway (1" tall) so the layers are not too big. The calculator is formulated for 2" tall layers. 
Important Things To Note Before You Start
1. Bring all your ingredients to room temperature or even a little warm (eggs, buttermilk, butter, etc) to ensure your batter does not break or curdle. 
2. Use a scale to weigh your ingredients (including liquids) unless otherwise instructed (Tablespoons, teaspoons, pinch etc). Metric measurements are available in the recipe card. Scaled ingredients are much more accurate than using cups and help ensure the success of your recipe. 
3. Practice Mise en Place (everything in it's place). Measure out your ingredients ahead of time and have them ready before you start mixing to reduce the chances of accidentally leaving something out.
4. Chill your cakes before frosting and filling. You can cover a frosted and chilled cake in fondant if you wish. This cake is also great for stacking. I always keep my cakes chilled in the refrigerator before delivery for easy transporting. Learn more about decorating your first cake. 
5. If the recipe calls for specific ingredients like cake flour, replacing it with all purpose flour and cornstarch is not recommended unless specified in the recipe that it’s ok. Substituting ingredients may cause this recipe to fail. 
All purpose flour is a plain flour with no rising agents. It has a protein level of 10%-12%
Cake flour is a soft, low protein flour of 9% or less. 
Cake flour sources: UK - Shipton Mills Cake & Pastry Flour

Nutrition

Serving: 1serving | Calories: 853kcal (43%) | Carbohydrates: 92g (31%) | Protein: 7g (14%) | Fat: 52g (80%) | Saturated Fat: 34g (170%) | Cholesterol: 115mg (38%) | Sodium: 365mg (15%) | Potassium: 207mg (6%) | Fiber: 1g (4%) | Sugar: 70g (78%) | Vitamin A: 1416IU (28%) | Calcium: 97mg (10%) | Iron: 1mg (6%)