Prepare and bake your favorite flavor (2-layer-size) cake mix, using 1 (8-inch) round and 1 (8-inch) square cake pan. Cool layers 10 minutes; remove from pans and cool completely on wire racks. Place square cake layer on large serving plate. Cut round cake in half; place 1 half next to square layer, placing straight sides together. Place remaining round cake layer half next to adjoining side of square layer to form heart shape. Frost and decorate as desired.