In a mixing bowl, using an electric mixer on medium-high speed, beat sugar and butter until light and fluffy, about 3 minutes. Add eggs and mashed banana and mix until well-combined.
In a small bowl, combine vinegar and milk. When milk begins to curdle, add to banana mixture and mix until well combined.
In a medium bowl, whisk together flour and baking soda. Reduce mixer speed to low, add flour mixture and mix until just combined. Fold in walnuts.
Pour batter into prepared pan and bake until a toothpick inserted in center comes out clean, about 1 hour. Remove from oven to a wire rack and cool. Invert pan to release bread, slice and serve.
Nutrition information per serving of 12:
Calories250Fat9 gSodium170 mg