Make a beautiful heart cake with these easy steps, using a basic square and round cake pan. Then frost and decorate to your heart's content! The recipe works well with any boxed cake mix or your favorite cake recipe. Here we're using the same chocolate cake recipe in my Chocolate Cake with Marshmallow Frosting recipe.
Make the cake batter according to the chocolate cake recipe. Preheat the oven accordingly as well.
Spray or coat the 8" square cake pan and the 8" round cake pan with baking spray or butter. Then dust the pans with a tablespoon of flour and knock out any excess.
Divide the batter evenly between the two pans. Bake until a toothpick inserted into the center of each cake comes out clean, and the cake bounces back when gently tapped in the centers with your fingertips.
Remove the cakes from the oven and cool 10 minutes. Run a knife around the perimeter of the cakes inside the pans and shake the cakes from side to side in the pans to help loosen them. Remove the cakes from the pans, flipping each cake onto a sheet of wax paper on a cutting board, plate or rack. Cool completely.
Make the raspberry buttercream according to the instructions. Set aside.
Set the square cake on the diagonal on a serving platter that is at least 14 inches square, so the heart cake will fit. Use platter, a cake board, or overturned sheet pan covered in foil.
Use a large serrated knife to cut the 8-inch round in half. These halves will make the top of the heart.
Set one half of the round against the top left side of the square cake that is already on the board, and then the second half against the top right side of the cake.