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–+ servings

Funfetti Cake

A soft, fluffy vanilla funfetti cake made with upgraded cake mix, layered with silky vanilla buttercream and overflowing rainbow jimmies hidden inside every slice. This easy semi-homemade recipe transforms a simple boxed mix into a bakery-style celebration cake with rich flavor, extra moisture, and the perfect dramatic sprinkle center.
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Course Dessert
Servings 13 slices

Equipment

  • 3 8-inch cake pans
  • Mixing Bowls
  • Stand mixer or hand mixer
  • Offset spatula
  • Serrated knife or cake leveler
  • Round cookie cutter or glass for center holes

Ingredients
  

Funfetti Cake Layers

  • 1 box Bob's Red Mill Vanilla Yellow Cake Mix
  • 1 additional cup cake flour
  • 4 large eggs
  • 1 cup whole milk
  • 1/2 cup neutral oil
  • 3/4 cup rainbow jimmies sprinkles

Sprinkle Center Filling

  • 1 1/2-2 cups rainbow jimmies sprinkles

Vanilla Buttercream Frosting

  • 4 sticks 2 cups unsalted butter, softened
  • 6-7 cups powdered sugar
  • 1/3 cup hot water
  • 2 teaspoons vanilla bean paste
  • 1/2 teaspoon salt

Instructions
 

Make the Cake Layers

  • Preheat the oven to 350°F (175°C). Grease and line three 8-inch cake pans with parchment paper.
  • In a large mixing bowl, whisk together the cake mix, cake flour, and salt.
  • Add the eggs, whole milk, sour cream, melted butter, oil, and vanilla bean paste. Mix until smooth and fully combined.
  • Gently fold in the rainbow jimmies sprinkles, being careful not to overmix.
  • Divide the batter evenly between the prepared cake pans.
  • Bake for 25–30 minutes, or until a toothpick inserted into the center comes out clean.
  • Let the cakes cool in the pans for 10–15 minutes before transferring to wire racks to cool completely.

Make the Hot Sugar Buttercream

  • In a medium bowl, whisk together the powdered sugar and hot water until smooth and glossy. The mixture should resemble a thick glaze.
  • In a stand mixer fitted with the paddle attachment, beat the softened butter on medium-high speed for 5–7 minutes until extremely pale, light, and fluffy.
  • Slowly pour the warm sugar mixture into the whipped butter while mixing on low speed.
  • Add the vanilla bean paste and salt, then continue whipping for another 3–4 minutes until smooth, silky, and airy.

Assemble the Cake

  • Level the cake layers if necessary.
  • Using a round cutter or glass, cut a hole in the center of the two bottom cake layers. Leave the top layer whole.
  • Place the first cake layer onto a cake stand or serving plate and spread an even layer of buttercream on top.
  • Add the second hollowed layer and frost the top again.
  • Fill the center cavity generously with rainbow jimmies sprinkles until completely full and slightly overflowing.
  • Place the final full cake layer on top to seal in the sprinkle center.
  • Frost the outside of the cake with the remaining buttercream.
  • Decorate with extra sprinkles around the edges and top of the cake if desired.

Notes

Cozy Baking Tips
  • Only use jimmies sprinkles in the batter to prevent color bleeding.
  • Chill the cake layers before assembling for cleaner frosting.
  • Use room temperature ingredients for the smoothest batter.
  • For extra clean slices, chill the assembled cake for 20–30 minutes before cutting.
Storage
  • Store the cake covered at room temperature for up to 2 days or refrigerated for up to 5 days. Let slices come
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