Preheat oven to 350*F. Prep a 9x5 loaf pan by spraying the bottom only with cooking spray.
In a large mixing bowl, cream together the sugar and butter. Then add eggs and beat well.
Add mashed bananas, buttermilk, and vanilla, and beat well until smooth.
In a separate bowl combine flour, baking soda and salt. Then pour into the banana mixture and beat until just combined.
Pour into prepared loaf pan. Bake for 1 hour and 15 minutes, or until a toothpick inserted into the center of the loaf comes back out clean. Cool for about 1 hour before slicing into 1/2 inch slices.