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slice of rainbow cake on blue plate white background and whole cake in background
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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.
Course Dessert
Cuisine American
Keyword easy buttercream, rainbow, white velvet
Prep Time 20 minutes
Cook Time 20 minutes
Total Time 40 minutes
Servings 14 cups
Calories 853kcal

Equipment

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

Ingredients

Rainbow Cake Ingredients

  • 24 oz cake flour
  • 24 oz granulated sugar
  • 1 tsp salt
  • 2 Tbsp baking powder
  • 1 tsp 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 tsp vanilla extract
  • 1/2 tsp 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 tsp Truly mad plastics super gold dust
  • 1/4 tsp 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. 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

Video

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 | Carbohydrates: 92g | Protein: 7g | Fat: 52g | Saturated Fat: 34g | Cholesterol: 115mg | Sodium: 365mg | Potassium: 207mg | Fiber: 1g | Sugar: 70g | Vitamin A: 1416IU | Calcium: 97mg | Iron: 1mg