In a large bowl, mix together banana, mayonnaise, egg, and vanilla.
In a medium bowl, whisk together flour, sugar, nuts, baking soda, and salt.
Add flour mixture to banana mixture and stir until just combined.
Bake 60-70 minutes, or until a toothpick comes out clean. Cool for 15 minutes in the pan then place on a cooling rack. Cool completely. Slice and serve!
Nutrition information does not include optional ingredients or garnish and is an estimate. It may change based on actual ingredients and cooking methods used.