Heat oven to 350. Grease bottoms only of 2 (8x4) or 1 (9x5) inch loaf pan.
In a large bowl, mix sugar nad butter. Add eggs, bananas, buttermilk, and vanilla; beat with electric mixer on medium sppeed until smooth. Stir in flour, baking soda, salt and nuts just until moistened. Pout batter into pans.
Bake 8-inch loaves 1 hour, 9-inch loaves 1 1/4 hours, or until toothpick inserted in center comes out clean. Cool 10 minutes. Loosen sides of loaves from pans; remove from pans to cooling rack. Cool about 1 hour before slicing.