This is really really good and very easy.
1/2 cup butter
3/4 cup brown sugar
3/4 cup sugar
1 cup mashed very ripe bananas (I often use about 3.5 ripe bananas, which I think is more than 1 cup)
2 large eggs
1 tsp vanilla
2 cups cake flour
1 tsp baking soda
1/2 tsp salt
1/2 cup sour cream (or use yogurt if you want to be virtuous)
Preheat oven to 350. Grease a 9" square pan.
Cream butter and sugar. Add bananas, eggs and vanilla. Beat well. Add dry ingredients and mix. Add milk and beat until well blended. Pour into prepared pan.
Bake 45 minutes or until done.
I am pretty sure that I have baked this in small loaf pans as well. I can't recall how long. I guess you'll have to figure that out.