Preheat the oven to 325.
Grease a 9x5x3 loaf pan and dust with flour.
Blend together the flour, baking soda and salt and set aside.
Mix together the egg, sugar, and vegetable oil until combined.
Add the flour mixture and when blended and add the buttermilk, vanilla, and mashed bananas and mix until combined.
Fold in 1/2 of the chopped walnuts and pour batter into prepared loaf pan.
Top batter with remaining walnuts.
Bake for 45 to 60 minutes, until a toothpick inserted in the center, comes out clean.
Cool for 10 minutes on a wire rack before removing from pan.