Preheat oven to 350 degrees F. Grease and flour a 9 1/2 by 5 1/2-inch loaf pan.
In a large mixing bowl, sift flour, whole-wheat flour, baking powder, and baking soda. Reserve.
In the bowl of an electric mixer, food processor, or blender, add eggs, butter, buttermilk, lemon juice, bananas, sugar, and salt.
Mix or blend until smooth. Slowly add dry ingredients. Fold in nuts. Pour batter into pan and bake 1 hour and 25 minutes or until toothpick inserted comes out clean.