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The Best Vanilla Funfetti Cake

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Classic Funfetti Cake filled with rainbow sprinkles and frosted in a smooth vanilla buttercream - perfect for any birthday party or fun celebration!
Servings 12 slices
Author Mandy Merriman - Baking with Blondie

Ingredients

Funfetti Cake Layers

  • 3/4 cup buttermilk room temperature
  • 2/3 cup sour cream room temperature
  • 4 egg whites room temperature
  • 1/3 cup vegetable oil
  • 1 Tablespoon vanilla
  • 1 15.25oz Classic White Cake Mix I prefer the taste and texture of Duncan Hines, but if you use anything similar it should be fine.
  • 1/2 cup rainbow sprinkles/jimmies

Vanilla Buttercream

  • 1 1/2 cup unsalted butter left out at room temperature for 10 minutes
  • 1 pinch salt
  • 1 Tablespoon pure vanilla
  • 1/4 cup heavy cream
  • 7-8 cups powdered sugar

Extra

  • 3 cups rainbow sprinkles

Instructions

For the funfetti cake Layers

  • Preheat the oven to 325 degrees. Prep two 8" cake pans (or three 6" cake pans) with a swipe of shortening and dust of flour to prevent sticking. Set aside.
  • In a large bowl, hand whisk together all the ingredients except for the cake mix and sprinkles. Sift in the cake mix and gently stir to combine. Fold in the sprinkles, then split the cake batter between the prepared cake rounds. Bake for 25-27 minutes. Flip the cakes out onto a wire rack to cool completely, then wrap up in plastic wrap to freeze until assembly. Before frosting, I sliced my 8" cake rounds in half so that I would have 4 skinny layers, but you can skip this step and just have two rounds if that's easier.

For the vanilla buttercream

  • In a stand mixer fitted with a paddle attachment, whip up the butter until it's light and fluffy, then add in the salt, vanilla, and heavy cream. Whip up again.
  • With the mixer speed on low, slowly add in the powdered sugar until it's all incorporated, then add in a touch more heavy cream if needed. Flip the stand mixer onto the highest speed and whip up until it's lightened in texture, about 2 minutes.

Assembly

  • On a cake turntable with a cardboard cake round, spread on a little buttercream in the middle, then put down the first cake round. Spread on a generous amount of buttercream, then place down the next cake layer.
  • Crumb coat the cake by applying a thin layer of buttercream. Freeze for 5 minutes.
  • Use a wooden spoon to beat out any air bubbles in the remaining buttercream, then spread on the rest of the buttercream on the top and sides of the cake. Use an offset icing spatula and a turntable to make the swirl on top, then use a cake scraper to make smooth sides on the outside.
  • Place the cake onto a cookie sheet, then place the cookie sheet onto the cake turntable. The cookie sheet will catch any sprinkles that don't stick to the cake! Slowly and gently press on the sprinkles around the outside of the cake until it's covered. Enjoy!