Set your oven to 350°F (175°C) and prepare two 9-inch round pans by greasing and dusting them with flour.
Beat the butter and sugar until you achieve a light and fluffy consistency. Add the eggs one by one, mixing after each addition, then add the vanilla.
Combine flour, baking powder, and salt. Add the dry ingredients and milk alternately, finishing with the dry ingredients.
Split the batter between two bowls. Use gel to color one of the bowls pink or blue.
Evenly divide the batter and pour into pans to create layers of white and colored batter. Bake for 25-30 minutes, then perform the toothpick test to check if the cake is done.
Awesome all the way. Use a stencil to shape a cake into an animal.
Apply a crumb coat with the buttercream, chill for 20 minutes, then finish with fondant or detailed frosting.
When cut at the party, the colored center shows the gender.