Heat the oven to 350 F. Prepare a 5-by-9-inch loaf pan by spraying it lightly with cooking spray. Dust with a little of any of the flours. Set aside.
In a large bowl, mix all dry ingredients except sugar together. In a separate bowl, combine egg, oil, sugar and mashed banana. Mix well. Add wet mixture to dry ingredients and combine thoroughly. Spoon into loaf pan. Bake for 50 to 60 minutes.
Check for doneness with toothpick — when the toothpick is removed it shouldn't have any batter sticking to it. Remove bread from oven, cool, slice and serve.