# What You Need:
→ Cake
01 - 2 1/2 cups all-purpose flour
02 - 2 1/2 teaspoons baking powder
03 - 1/2 teaspoon baking soda
04 - 1/2 teaspoon salt
05 - 1 cup unsalted butter, room temperature
06 - 1 1/2 cups granulated sugar
07 - 4 large eggs, room temperature
08 - 2 teaspoons pure vanilla extract
09 - 1 cup whole milk, room temperature
10 - 1/2 cup sour cream, room temperature
11 - 2/3 cup rainbow sprinkles
→ Pastel Buttercream
12 - 1 1/2 cups unsalted butter, room temperature
13 - 5 cups powdered sugar, sifted
14 - 1/4 cup whole milk
15 - 2 teaspoons pure vanilla extract
16 - Pinch of salt
17 - Pastel food coloring gels in pink, blue, yellow, and purple
# Steps:
01 - Preheat oven to 350°F. Grease and line two 9-inch round cake pans with parchment paper.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt.
03 - In a large bowl, beat butter and sugar together until light and fluffy, approximately 3 minutes.
04 - Add eggs one at a time, beating well after each addition. Mix in vanilla extract.
05 - In a separate bowl, whisk milk and sour cream until combined.
06 - Add the flour mixture to the butter mixture in three parts, alternating with the milk mixture, beginning and ending with flour. Mix just until combined.
07 - Gently fold in the rainbow sprinkles with a spatula.
08 - Divide batter evenly between the prepared pans and smooth the tops.
09 - Bake for 28 to 32 minutes, or until a toothpick inserted into the center comes out clean.
10 - Cool cakes in pans for 10 minutes, then turn onto a wire rack to cool completely.
11 - Beat butter until smooth and creamy, approximately 2 minutes.
12 - Gradually add powdered sugar, mixing on low speed until incorporated.
13 - Add milk, vanilla, and salt. Beat on high speed until fluffy, 2 to 3 minutes.
14 - Divide buttercream into 4 bowls. Tint each with a different pastel food coloring gel.
15 - Dollop or pipe colored buttercream onto cooled cake layers as desired. Swirl colors together to create a marbled pastel effect.
