1. Preheat oven to 350°F. Grease and flour two 9-inch round cake pans.
2. Combine cake mix, water, eggs and oil in large bowl. Beat at low speed with electric mixer until moistened. Beat at medium speed 2 minutes. Stir in bananas. Pour into prepared pans. Bake at 350°F for 28 to 31 minutes or until toothpick inserted into center comes out clean. Cool in pans 15 minutes. Remove from pans; cool completely.
3. Fill and frost cake with frosting. Garnish as desired.