Preheat the oven to 350°F (175°C).
Grease and flour two 9-inch round cake pans.
Cream together butter and sugar until light and fluffy.
Add eggs one at a time, mixing well after each addition.
Stir in milk and vanilla extract.
In a separate bowl, combine flour and baking powder.
Gradually add dry ingredients to wet ingredients and mix until combined.
Divide batter into two bowls; color one with red food coloring and the other with pink.
Pour each batter into prepared pans and bake for 25 to 30 minutes.
Let cakes cool completely before applying buttercream frosting.
Decorate with buttercream frosting and fondant to create the Hello Kitty design.