- Preheat oven to 350 degrees, spray bottom only of a 9 x 5 x 3 loaf pan with nonstick cooking spray.
- Beat butter in large bowl with an electric mixer set at medium speed until light and fluffy. Add sugar and brown sugar; beat well. Add egg, egg whites and vanilla; beat well until well blended. Add mashed banana, and beat on high speed 30 seconds.
- Combine in a medium bowl baking soda, baking powder and salt.