Preheat the Oven: Heat your oven to 375°F (190°C) and grease a 9x5-inch loaf pan or line it with parchment paper.
Mix Wet Ingredients: In a large bowl, mash the bananas until smooth. Stir in the melted butter, sugar, eggs, and vanilla extract until well combined.
Prepare Dry Ingredients: In a separate bowl, combine the flour, baking powder, baking soda, salt, and cinnamon. Whisk until evenly distributed.
Combine and Fold: Gradually add the dry ingredients into the wet mixture, folding gently until just combined. Be careful not to overmix. Fold in the chopped walnuts.
Pour and Bake: Pour the batter into the prepared loaf pan. Sprinkle extra chopped walnuts on top. Bake for 45-55 minutes, or until a toothpick inserted into the center comes out clean.
Check for Browning: If the top is browning too quickly, cover it loosely with foil to prevent burning.
Cool and Serve: Allow the bread to cool in the pan for 10-15 minutes, then transfer it to a wire rack to cool completely before slicing.