Preheat the oven to 350°F. Mix butter and bananas in a large mixing bowl until combined. Add sugar, egg, vanilla; mix well. Add baking soda and salt and mix. Add the flour last, and mix until just combined. You don't want to over mix. Add nuts if desired.
Pour mixture into a buttered 4x8 inch loaf pan or muffin tin. Bake for 50-55 minutes for the loaf, or 22-25 minutes for the muffins. Test with toothpick for doneness.
Cool on a rack. Remove from pan and slice to serve. Top with butter or cream cheese and enjoy!
For a bit of a healthier take, divide flour and use 3/4 cup white flour and 3/4 cup whole wheat flour. Still comes out delicious!