I first found this recipe in our community church cookbook. That book has disappeared, but the recipe lives on.
1/3 c butter or margarine
1 c sugar
2 eggs
1 tsp soda
1 tsp baking powder
1 tsp cream of tartar
½ tsp salt
1 ½ c flour
3-4 mashed bananas
Mix all the ingredients well using beaters. Pour batter in a greased loaf pan. Bake in 350 degree oven for about an hour. Test for doneness using a toothpick, when inserted comes out cleanly.