1 - Preheat oven to 350F. Lightly coat 9 by 5 loaf pan with nonstick baking spray.
2 - In medium bowl, whisk flour, baking powder, baking soda, salt, and cinnamon.
3 - In large bowl, with mixer on medium-high speed, beat sugar, egg whites, and egg until almost double in volume. On medium-speed, beat in bananas, buttermilk, and oil until well combined.
4 - With rubber spatula, gently fold in flour mixture until just combined.
5 - Pour batter into prepared pan, smoothing top. Bake 1 hour or until toothpick inserted in center comes out clean.
6 - Let cool in pan on wire rack 10 minutes. Remove from pan and let cool completely on wire rack. Can be stored, tightly wrapped, at room temperature up to 3 days or in freezer up to 1 month.
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