Preheat oven to 350 degrees. Grease and flour one 9-inch loaf pan (or 3 small ones). Pan should be ¾ full of batter.
In a large bowl, cream the butter with sugar until light and fluffy. Add the eggs and mix well.
Whisk together the flour, baking soda, and salt; combine with the butter mixture.
Add the sour cream, bananas, and vanilla; stir well.
Pour into prepared pans and bake for 50-55 minutes.
Cool for 10 minutes and then turn the loaf out onto a rack.
