Bake and cool your favorite 1-layer sheet cake. Position cake on foil-covered cake board. Spatula ice cake smooth with buttercream icing; ice sides of cake at least 1/2-inch thick.
Comb sides of cake using small-tooth edge of decorating comb. Roll out red fondant 1/8-in. thick. Cut out an "A" with cookie cutter; cut out 2 smaller "A"s with alphabet cut-out. Using heart cut-outs, cut out 1 large and 2 small fondant hearts. Attach all fondant pieces to cake.