Step 1: Preheat your oven to 350°F (175°C). Grease and flour a 9×5-inch loaf pan, or line it with parchment paper, leaving an overhang on the sides for easy removal.
Step 2: In a large bowl, mash the ripe bananas thoroughly with a fork or potato masher until mostly smooth with a few small lumps remaining. The lumpier your bananas, the more texture you’ll have in the final bread.
Step 3: Add the melted butter to the mashed bananas and stir to combine. Then, stir in the baking soda, salt, and granulated sugar until well mixed.
Step 4: Beat in the large egg and vanilla extract until fully incorporated into the banana mixture.
Step 5: Gradually add the all-purpose flour to the wet ingredients, mixing until just combined. Be careful not to overmix; a few streaks of flour are okay. Fold in the chopped walnuts if using.
Step 6: Pour the batter into the prepared loaf pan. If desired, sprinkle a few extra chopped walnuts on top for decoration.
Step 7: Bake for 55-65 minutes, or until a wooden skewer inserted into the center of the loaf comes out clean. If the top starts to brown too quickly, you can loosely tent it with aluminum foil.
Step 8: Once baked, remove the loaf from the oven and let it cool in the pan for 10-15 minutes before carefully lifting it out by the parchment paper overhang onto a wire rack to cool completely. Slicing too early can cause it to crumble.