Ingredients:
For the cake:
2 1/2 cups all-purpose flour
2 1/2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1 cup unsalted butter, softened
1 3/4 cups granulated sugar
4 large eggs
1 tablespoon vanilla extract
1 cup buttermilk, room temperature
1/2 cup sour cream, room temperature
3/4 cup rainbow sprinkles (jimmies, not nonpareils)
For the frosting:
1 1/2 cups unsalted butter, softened
5 cups powdered sugar
2 teaspoons vanilla extract
2–4 tablespoons heavy cream or milk
Pinch of salt
For decorating:
Additional rainbow sprinkles
Buttercream rosettes or stars for topping
Instructions:
Preheat the oven to 350°F (175°C). Grease and line three 8-inch round cake pans with parchment paper.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
In a large mixing bowl, beat the softened butter and sugar together until light and fluffy, about 3–4 minutes.
Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.
Add half of the flour mixture, followed by the buttermilk and sour cream, then the remaining flour mixture. Mix until just combined.
Fold in the rainbow sprinkles gently with a spatula.
Divide the batter evenly between the prepared pans and smooth the tops. Bake for 25–28 minutes or until a toothpick inserted in the center comes out clean.
Cool the cakes in the pans for 10 minutes before turning them out onto wire racks to cool completely.
To make the frosting, beat the butter until creamy. Gradually add the powdered sugar, vanilla, and a pinch of salt. Add heavy cream a tablespoon at a time until you reach a spreadable consistency.
Layer the cakes with frosting between each layer. Frost the top with an even layer, leaving the sides exposed for a “naked cake” style.
Pipe buttercream rosettes or stars on the top using a star tip and sprinkle generously with rainbow sprinkles.
Decoration Tips:
– Use jimmies inside the batter to avoid color bleeding. They bake evenly and keep their shape.
– When decorating the top, alternate piped rosettes and stars for texture. Use a large open star piping tip for bold, clean shapes.
– Don’t forget the base of the cake press sprinkles into the bottom edge for a festive border effect.
– For extra flair, chill the frosted cake for 15 minutes before adding the final layer of sprinkles so they sit nicely without smudging the buttercream.
– Present the cake on a white or pastel cake stand for contrast and let the colors pop. A sprinkle-covered cake board also adds charm without effort.
Happy Baking
