Preheat oven to 350°F.
In a mixing bowl, combine the melted butter, sugar, eggs and vanilla with a hand mixer.
Next, add the flour, baking soda and salt then mix to combine.
Next, add the mashed bananas and mix to combine.
Next, add the mayonnaise (or sour cream) and mix into the batter.
Stir in the toasted pecans.
Spray a loaf pan with cooking spray then pour in the batter.
Bake the banana bread 45 minutes to 1 hour, or until a toothpick comes out clean when inserted in the middle of the bread.
Allow the bread to cool then transfer out of the loaf pan to cool completely.