1. preheat oven to 350 and spray a 13 x 9 inch baking ban with cooking spray
2. on a sheet of wax paper, sift together flour, baking powder, baking soda, salt and nutmeg. Set aside
3. In large mixing bowl, using an electric mixer set on high speed, beat together 1 1/4 cups of sugar, and butter until creamy. Add eggs and egg whites, one at a time, beating well after each addition. Alternately stir in flour mixture and milk. Stir in bananas and walnuts.
4. Spread batter in prepared pan. Sprinkle evenly with remaining sugar.
5. Bake cake until top is golden brown and a toothpick inserted in center comes otu almost clean, about 40 minutes. Cool.