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 flour, baking powder, and salt. Set aside.
03 - In a large bowl, beat the softened butter and granulated sugar using an electric mixer until light and fluffy, about 3-4 minutes.
04 - Add eggs one at a time, beating well after each addition. Mix in the cotton candy flavoring and vanilla extract until fully incorporated.
05 - With the mixer on low speed, add the flour mixture in three parts, alternating with the milk, beginning and ending with the flour. Mix until just combined; do not overmix.
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, then swirl gently with a skewer or knife for a marbled effect.
07 - Bake for 25-28 minutes, or until a toothpick inserted into the center comes out clean. Cool the cakes in the pans for 10 minutes, then invert onto a wire rack to cool completely.
08 - Beat the butter until creamy and smooth. Gradually add the powdered sugar on low speed, then increase to medium. Blend in the cotton candy flavoring and milk until the frosting is light and fluffy. Divide the buttercream and tint pink and blue as desired.
09 - Once the cake layers are completely cool, stack and frost with the buttercream. Swirl the pink and blue frosting together for a cotton candy effect on the exterior.
10 - Just before serving, crown the cake with fluffy pieces of fresh cotton candy. Serve immediately to preserve the cotton candy texture.