Prepare Oven & Pan: Preheat your oven to 350°F (175°C). Lightly grease and flour a 9x5 inch loaf pan, or line with parchment paper for easy removal.
Mash Bananas: In a large bowl, mash the ripe bananas with a fork or potato masher until mostly smooth with a few small lumps remaining.
Combine Wet Ingredients: Add the melted butter to the mashed bananas and stir until well combined. Then, mix in the granulated sugar, lightly beaten egg, and vanilla extract until the mixture is uniform.
Combine Dry Ingredients: In a separate medium bowl, whisk together the all-purpose flour, baking soda, and salt.
Combine Wet & Dry: Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix; a few streaks of flour are fine. Overmixing can lead to tough banana bread.
Fold in Walnuts: Gently fold in the chopped walnuts until evenly distributed throughout the batter.
Bake: Pour the batter into the prepared loaf pan and spread evenly. Bake for 50-65 minutes, or until a wooden skewer or toothpick inserted into the center comes out clean or with a few moist crumbs attached.
Cool & Serve: Let the Banana Bread with Walnuts cool in the loaf pan for 10 minutes before carefully transferring it to a wire rack to cool completely. Slice and serve as desired.