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Rainbow Birthday Cake | An impressive rainbow frosted cake that is perfect for any anniversary, birthday or special occasion. A classic vanilla cake recipe is finished off with multi-color buttercream frosting!
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5 from 2 votes

Rainbow Birthday Cake

This rainbow decorated cake is a perfect addition to a birthday party. 
Prep Time45 minutes
Cook Time30 minutes
Total Time4 hours 15 minutes
Course: Dessert
Cuisine: American
Servings: 24 servings


Buttermilk White Cake

  • 2 c. butter melted
  • 4 c. sugar
  • 6 eggs
  • 2 t. vanilla extract
  • ½ t. almond extract
  • 2 ⅔ c. white rice flour
  • 1 ⅓ c. tapioca starch
  • 2 t. xanthan gum
  • Or 4 c. all purpose flour instead of the above 3 ingredients
  • 2 ½ t. baking powder
  • ½ t. salt
  • 1 ⅓ c. buttermilk

Buttercream Frosting (multiply recipe by 2 ½)

  • ½ c. butter
  • 6 c. powdered sugar
  • 1 egg white
  • 3-4 T. milk
  • 2 t. vanilla clear
  • ½ t. salt
  • Food coloring if desired (first batch (1x above recipe) all white for crumb coating, second batch (1.5x above recipe) for rainbow colors)

Piping Tutorial:

  • 4-6 piping bags
  • 4-6 couplers
  • 4-6 size 12 round piping tips


For the Buttermilk White Cake:

  • Preheat oven to 350 degrees.
  • If you have a bowl that fits at least 12 cups of ingredients, go ahead and make this batch as the ingredients are listed above for a 4-layered cake. However, if you do not, halve the ingredients and make two batches. (Half of ⅓ c. = 3 T.+1 t. )
  • Combine butter and sugar in a large bowl of a high speed mixer. Mix for 2 minutes on medium speed.
  • In a separate bowl, combine white rice flour, tapioca starch, xanthan gum, baking powder, and salt. Add in about 1 c. of dry ingredients to the butter/sugar bowl. Mix for 30 seconds.
  • Add eggs, one at a time, mixing well after each addition. Add in vanilla and almond extract.
  • Add remaining dry ingredients and buttermilk alternatively, starting and ending with dry ingredients. Beat for an additional minute to make batter light and fluffy.
  • Fill four well-greased 9-inch round cake pans with even amounts of cake batter. Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
  • Let cool for 5-10 minutes before flipping out.

For the Buttercream Frosting:

  • Cream butter, 2 c. powdered sugar and egg white in the bowl of an electric mixer.
  • Alternatively add 1 c. sugar and 1 T. milk until all sugar is added.
  • Add in vanilla, salt and food coloring, if desired.

For the Cake Prep:

  • Prep your cake for the rainbow icing instructional video by using the first batch of frosting. Place the first layer down, ice the top with a ¼- ½ inch layer of frosting and repeat with the remaining 3 layers.
  • Trim any uneven edges around the cake and finish the cake prep by applying the remainder of the frosting on the sides of the cake.


Calories: 724kcal | Carbohydrates: 131g | Protein: 3g | Fat: 21g | Saturated Fat: 13g | Cholesterol: 95mg | Sodium: 227mg | Potassium: 62mg | Sugar: 97g | Vitamin A: 695IU | Calcium: 30mg | Iron: 0.5mg