Prepare the Cake Batter
Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans. In a medium bowl, whisk together the flour, baking powder, and salt.

Cream Butter and Sugar
In a large bowl, using an electric mixer, beat the softened butter and granulated sugar until light and fluffy, about 3-4 minutes.

Add Egg Whites and Vanilla
Add the egg whites to the butter-sugar mixture one at a time, beating well after each addition. Mix in the clear vanilla extract.

Combine Dry Ingredients and Buttermilk
Alternately add the dry ingredient mixture and buttermilk to the batter, beginning and ending with the dry ingredients. Mix until just combined; do not overmix.

Fold in Sprinkles
Gently fold in the pastel confetti sprinkles, being careful not to overmix to prevent color bleeding.

Bake the Cakes
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 minutes, then remove from pans and transfer to a wire rack to cool completely.

Prepare the Frosting
In a large bowl, beat the softened butter until creamy. Gradually add the powdered sugar, mixing on low speed until combined. Add the clear vanilla extract and a pinch of salt. Increase the mixer speed to medium and beat until fluffy, adding heavy cream as needed to reach the desired consistency.

Assemble and Frost the Cake
Place one cake layer on a serving plate. Spread a layer of frosting on top. Place the second cake layer on top and frost the top and sides of the cake. Decorate with additional pastel sprinkles as desired.