01 - Preheat the oven to 350°F. Grease and line three 8-inch round cake pans with parchment paper.
02 - In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.
03 - In a large bowl, beat the softened butter and granulated sugar together using an electric mixer until light and fluffy, about 3 to 4 minutes.
04 - Add the eggs one at a time, beating well after each addition. Mix in the cotton candy flavoring and vanilla extract until evenly combined.
05 - With the mixer on low speed, add the flour mixture in three parts, alternating with the whole milk, beginning and ending with the flour. Mix until just combined.
06 - Divide the batter evenly into two bowls. Tint one portion pink and the other blue using food coloring. Drop spoonfuls of each color alternately into the prepared pans for a marbled effect, then swirl gently with a skewer or knife.
07 - Bake for 25 to 28 minutes, or until a toothpick inserted into the center comes out clean. Cool the cakes in the pans for 10 minutes, then turn out onto a wire rack to cool completely.
08 - Beat the butter until creamy. Gradually add the sifted powdered sugar on low speed, then mix in the cotton candy flavoring and milk until smooth and fluffy. Divide the buttercream and tint portions pink and blue as desired.
09 - Once the cake layers are completely cool, stack and frost with the colored buttercream. Swirl the pink and blue frosting together for a cotton candy effect.
10 - Just before serving, arrange fluffy pieces of fresh cotton candy on top of the frosted cake. Serve immediately to preserve the cotton candy texture.