Preheat your oven to 350 degrees. Spray a 9x5 loaf pan with non-stick baking spray and sprinkle 1 teaspoon sugar on it. Set the pan aside.Beat the butter until creamy. Add the sugar and beat again until light and fluffy.Add the eggs and vanilla and mix in.Stir together the flour, baking soda, and salt and slowly beat into the butter mixture.Stir in the banana and sour cream until completely incorporated.Spread the batter in the prepared pan and bake for 60-65 minutes, or until a toothpick comes out mostly clean. Let the bread cool in the pan for 10-15 minutes, then flip it out onto a cooling rack. Serve warm with butter, if desired. Store in a sealed container.