Preheat oven to 325. Grease a 9x5x3 loaf pan and dust with flour
Blend the flour, baking soda, and salt; set aside.
Mix the egg, sugar, and oil until combined.
Add the flour mixture to the egg mixture and when blended, add the buttermilk, vanilla and mashed bananas; mix well.
Mix some walnut into the batter and pour into pan; spread the remaining walnuts on top.
Bake for 45-60 minutes until a toothpick comes out clean.