01 - Preheat the oven to 350°F. Grease and flour a 9x5-inch loaf pan or line with parchment paper.
02 - In a large bowl, whisk together the mashed bananas, eggs, melted butter, buttermilk, and vanilla extract until smooth and uniform.
03 - In a separate bowl, combine the flour, granulated sugar, brown sugar, baking soda, salt, and ground cinnamon.
04 - Gently fold the dry mixture into the wet ingredients using a spatula. Stop as soon as just combined to avoid overmixing.
05 - Fold in the chopped walnuts or pecans until evenly distributed throughout the batter.
06 - Pour the batter into the prepared loaf pan and smooth the top. Sprinkle extra nuts on the surface if desired.
07 - Bake for 50 to 60 minutes, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs.
08 - Let the bread rest in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.