1. Heat oven to 325 degrees F.
2. Prepare cake mix following package directions, using the ingredients as indicated in the directions.
3. Coat 11-inch tart pan with removable bottom and 4-cup ovenproof bowl (6 inches across top) with nonstick cooking spray. Pour 3 cups cake batter into the prepared tart pan, filling about halfway. Pour the remaining batter, about 1-1/2 cups, into the prepared bowl.
4. In the 325 degrees F oven, bake the tart for about 20 to 25 minutes, and the bowl for about 30 to 35 minutes, or until a wooden pick inserted in centers comes out clean. Cool both tart pan and bowl on wire racks for 15 minutes. Unmold the cakes onto racks to cool completely. If necessary, trim top of bowl cake so it is flat and level.
5. Spoon both containers of frosting into large microwave-safe bowl. Whisk in 4 drops of food coloring or as many drops as needed for desired shade. Microwave the frosting on high power until good spreading consistency, about 30 seconds.
6. Spread frosting with metal spatula over tart cake; then spread frosting over inverted bowl cake. Reserve leftover frosting. Place cakes in refrigerator to set, about 20 minutes.
7. Place tart cake on a platter or aluminum-foil-covered cardboard. Place bowl cake, flat side down, on top of tart cake to form bonnet. Spread remaining frosting over entire cake for a finished surface. If frosting in bowl becomes too firm to spread, reheat in microwave oven as needed to keep frosting spreadable.
8. Wrap ribbon around base of hat and make decorative bow. Arrange flowers and leaves as pictured.