Preheat the oven to 350°F (175°C). Grease a 9 × 5-inch loaf pan with butter or cooking spray, or line it with parchment paper. Prepare the pan before mixing the batter so it is ready to use.
Peel the ripe bananas and place them in a large mixing bowl. Mash with a fork until mostly smooth, leaving a few small lumps if you prefer some banana texture. Very ripe bananas with brown spots provide the sweetest flavor and help keep the bread moist.
Add the applesauce, vegetable oil or melted butter, sugar, eggs, and vanilla extract to the mashed bananas. Whisk until the mixture is evenly combined. If using melted butter, allow it to cool slightly before mixing it with the eggs.
In a separate bowl, whisk together the flour, baking soda, cinnamon, and salt. Breaking up any lumps helps distribute the baking soda evenly, allowing the loaf to rise consistently during baking.
Add the dry ingredients to the banana mixture. Fold gently with a rubber spatula until no large streaks of flour remain. Stir in the optional walnuts or chocolate chips, if using. Avoid overmixing, as too much stirring can make the finished bread dense.
Pour the batter into the prepared loaf pan and spread it evenly. Smooth the top with a spatula so the bread bakes uniformly. If desired, sprinkle a few chopped walnuts over the surface for extra texture.
Bake for 50–60 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean or with a few moist crumbs. If the top browns too quickly, loosely cover the loaf with aluminum foil and continue baking until the center is cooked through.
Remove the pan from the oven and let the bread cool for 10–15 minutes. Carefully transfer the loaf to a wire rack and allow it to cool further before slicing. This helps the crumb set and makes it easier to cut neat slices without crumbling.