To begin, preheat your oven to 350 degrees. In a bowl, combine the flour, baking soda, baking powder and salt. Stir together and set aside for now. In your mixing bowl, combine the sugars and and butter. Beat those together until nice and creamy. Beat in the eggs, one at a time. Mix in a teaspoon of vanilla. In a small bowl, mash the bananas. After mashing them well, add them into the creamy mixture in your mixing bowl, and mix well. Mix in half of your dry ingredients.
Mix in the sour cream, and then the remaining dry ingredients.
Spread the batter into a greased loaf pan. Bake for 1 hour and 10 minutes or until a toothpick inserted in the center comes out clean. Allow the loaf to rest a couple minutes then remove to a cooling rack.