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Rainbow Unicorn Cake with Twinkie Filling by Let's Eat Cake
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Rainbow Unicorn Cake with Twinkie Filling

This whimsical unicorn cake is super festive with its layers of rainbow cake, vanilla frosting, and Twinkie filling!
Course Dessert
Cuisine American
Keyword rainbow unicorn cake
Prep Time 30 minutes
Cook Time 50 minutes
Total Time 1 hour 20 minutes
Servings 12
Author Rebecca Swanner

Ingredients

Rainbow Unicorn Cake Batter

  • 1 cup + 2 Tbsp. unsalted butter room temperature
  • 1¾ cup sugar
  • 3 cups all-purpose flour
  • 1 tsp. baking powder
  • ½ tsp. baking soda
  • ½ tsp. salt
  • 2 tsp. vanilla
  • 4 large eggs room temperature
  • 1 cup buttermilk
  • food coloring

Twinkie Filling

  • 1 (7.5-oz.) jar marshmallow fluff
  • ½ cup unsalted butter
  • 1 tsp. vanilla extract

Vanilla Frosting

  • 4 Tbsp. unsalted butter room temperature
  • 2 cups powdered sugar
  • 1 tsp. vanilla extract
  • ¼ cup whole milk
  • sprinkles

Instructions

Rainbow Unicorn Cake Batter

  • Preheat oven to 350°F.
  • Flour and butter bundt cake pan and set aside.
  • Cream butter and sugar together in stand mixer on medium-high to high for 5 minutes.
  • Meanwhile, combine flour, baking powder, baking soda, salt, and vanilla in small bowl.
  • Turn speed on mixer to medium. Add eggs, one at a time, to bowl. Let mix for 30 seconds before adding next egg.
  • Turn speed on mixer to low. Add 1/3 flour mixture. Add 1/2 cup buttermilk. Add second third of flour mixture. Add remaining buttermilk. Add remaining flour mixture. Let mix until just combined.
  • Divide batter into four bowls. Add coloring to each and mix with a spoon until combined. Layer batter into bundt cake pan, one color at a time.
  • Bake for 50-55 minutes until cake tester comes out clean.
  • Let cool for one hour on cooling rack with opening facing ceiling (batter side up).

Twinkie Filling

  • Invert cake - using cooling rack to help - to make sure cake comes out of bundt pan. Once it does, flip back over and create 8 equally-spaced holes in bottom of cake using round nozzle or thin knife. Using your fingers, gently create a tunnel between the holes in the middle of the cake.
  • Combine marshmallow fluff/creme, butter, and vanilla in stand mixer until fully combined.
  • Add filling to piping bag fitted with round nozzle. Pipe into each hole, piping until cake begins to puff up slightly.

Vanilla Frosting

  • Combine butter, confectioners sugar, and 2 tbsp. milk in bowl of stand mixer on medium high.
  • Add vanilla. Add milk, 1 tbsp. at a time, until desired consistency is achieved.
  • Frost cake and add sprinkles!