Using serrated knife, cut rounded top off cake to level surface; place cut side down. Cut cake in half; cut a notch on each cut side, slightly below center, to form wings as shown in diagram. To make butterfly, arrange 2 wings on foil-covered tray; use 2 of the leftover notched pieces to form the body, trimming if necessary. Attach pieces together with a small amount of frosting. Spread a thin layer of frosting over top and sides to seal in crumbs. Refrigerate or freeze cake 30 to 60 minutes to set frosting. Frost entire cake.