Preheat your oven to 350°F (175°C). Grease and flour three 8-inch round cake pans.
In a large bowl, cream together the softened butter and sugar until light and fluffy.
Add eggs one at a time, mixing well after each addition.
Stir in vanilla extract and mix until combined.
In another bowl, whisk together flour, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture, alternating with milk, until smooth.
Divide the batter into three bowls and color each with different food coloring.
Pour each colored batter into the prepared cake pans, layering the colors as desired.
Bake in the preheated oven for 25-30 minutes or until a toothpick comes out clean.
Allow cakes to cool in pans for 10 minutes before transferring to wire racks to cool completely.
Once cooled, frost the cakes with buttercream frosting, stacking them and decorating with fondant unicorn features.