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5 from 1 vote

Rainbow Cake

This gorgeous rainbow cake is the best way to add a splash of color to any special occasion! Not only is this cake beautiful to look at, but it’s extra moist and topped with luscious homemade buttercream. It’s the perfect dessert for birthdays, Saint Patrick’s Day, and more!
Prep Time1 hour
Cook Time18 minutes
Chill Time4 hours
Total Time5 hours 18 minutes
Course: Dessert
Cuisine: American
Keyword: layered rainbow cake, rainbow cake
Servings: 12 People
Author: Alyssa Rivers

Ingredients

Cake

  • 3 ⅓ cup cake flour
  • 2 ¼ cup granulated sugar
  • 2 ¼ teaspoon baking powder
  • ¾ teaspoon baking soda
  • 1 ½ cup buttermilk
  • ⅓ cup milk
  • 3 teaspoons vanilla extract
  • ¾ cup vegetable oil
  • 6 egg whites room temperature
  • Food coloring

Buttercream

  • 2 pounds unsalted butter room temperature
  • 16 cups powdered sugar
  • 2 tablespoons vanilla extract
  • 1 pinch salt
  • 1/3 cup heavy cream more if needed
  • Food coloring

Instructions

  • Preheat the oven to 350 degrees fahrenheit. Spray 6 8-inch cake pans with cooking spray and line with parchment rounds. If you don’t have 6 cake pans, use what you have and bake in batches. I baked two cakes at a time.
  • In a large bowl whisk together the flour, sugar, baking powder, and baking soda. Add in the buttermilk, milk, vanilla and oil and mix until just combined.
  • In another large bowl whip the egg whites until you reach medium stiff peaks.
  • Fold the egg whites into the batter until no streaks of whites remain. Separate the batter equally into 6 different bowls. I had about 275 grams of batter per bowl. Color the batter red, orange, yellow, green, blue, and purple.
  • Bake in prepared pans for 15-18 minutes, until the center of the cake springs back when lightly pressed on.
  • Let the cakes cool completely before wrapping with plastic wrap and stored flat in the freezer overnight. This will make them easier to stack and frost.

Buttercream

  • Beat the butter and powdered sugar together in a stand mixer until combined. Add the vanilla, salt and 4-5 tablespoons of cream. Beat until smooth. Add more cream if needed to reach a softer, smoother consistency.
  • Reserve 2 cups of white frosting, and tint the rest of it light blue.
  • Start with the purple cake round on the bottom and add a thin layer of frosting. Top with the blue round followed by a thin layer of frosting. Repeat with the rest of the rounds until you have them stacked purple, blue, green, yellow, orange, and finishing with red on top. Add a thin layer of frosting over the outside of the cake to form the crumb coat. Chill for 20 minutes.
  • Once the crumb coat has chilled, use a frosting spatula to smooth the frosting around the cake. Avoid lifting the spatula straight off the cake and instead swipe it along the cake until it comes off. This will help avoid pulling off the sides of the cake and getting crumbs in your buttercream.
  • Use a piping bag fitted with a very large round tip to pipe white clouds around the top and cascading over the top edge of the cake.

Nutrition

Calories: 1497kcal | Carbohydrates: 225g | Protein: 8g | Fat: 66g | Saturated Fat: 41g | Polyunsaturated Fat: 3g | Monounsaturated Fat: 17g | Trans Fat: 2g | Cholesterol: 174mg | Sodium: 146mg | Potassium: 219mg | Fiber: 1g | Sugar: 197g | Vitamin A: 2048IU | Vitamin C: 0.04mg | Calcium: 106mg | Iron: 1mg

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