In medium bowl cream butter and sugars together. Then add in mashed bananas, beaten eggs, applesauce & vanilla. Mix well.
Make well in dry ingredients and pour wet ingredients into well and mix together only until all ingredients are incorporated. Over mixing will cause the bread to be dry!
Bread does not rise much, so you can fill to within 1/2 inch or so of the top of the loaf pan. Add topping if you want at this time (although it is not needed).
Check doneness with toothpick in several places to make sure the bread is done. Allow to set in pan for 10 minutes, then (if you are sure it is done) remove from pan and allow to cool completely (if you can before you eat it all!)