Preheat the oven to 350F
In a large bowl, mix your over-rip mashed bananas, mayo, vanilla, and egg together until well combined
In a separate medium bowl, combine flour, sugar, baking soda, baking powder and salt
Next add in flour mixture to wet mixture and stir until its JUST combined - making sure NOT to over-mix because it will be thick
Pour into a greased and floured loaf pan 9x5 in size
Sprinkle chopped walnuts on top evenly
Bake 55-60 minutes or until a toothpick comes out clean from center
Remove from pan and allow to cool completely on a wire rack.
Slice & ENJOY!