Preheat your oven to 175°C (350°F). Grease and flour a standard loaf pan, approximately 23cm x 13cm (9 x 5 inches), or line it with parchment paper for easy removal. This ensures the banana bread doesn't stick and has a nice crust.

In a large bowl, mash the ripe bananas with a fork or potato masher until they are mostly smooth with a few small lumps remaining. Over-mashing can lead to a gummy texture.

Add the melted unsalted butter (115g or 1/2 cup), granulated sugar (150g or 3/4 cup), room temperature eggs (2 large), and vanilla extract (5ml or 1 tsp) to the mashed bananas. Whisk everything together until well combined and smooth. Ensure the butter is not too hot, or it might cook the eggs.

In a separate medium bowl, whisk together the sifted all-purpose flour (250g or 2 cups), baking soda (5g or 1 tsp), salt (2g or 1/4 tsp), and ground cinnamon (2.5g or 1/2 tsp, if using). Whisking the dry ingredients together ensures the leavening agent and salt are evenly distributed, preventing pockets of baking soda or salt in the final loaf.

Gradually add the dry ingredients to the wet ingredients. Mix with a spatula or wooden spoon until just combined. Be careful not to overmix; a few streaks of flour are acceptable. Overmixing develops gluten, which can result in a tough banana bread.

If using, gently fold in the chopped walnuts or pecans (100g or 1 cup) into the batter. Distribute them evenly throughout the batter.

Pour the batter into the prepared loaf pan, spreading it evenly. The batter will be thick.

Bake in the preheated oven at 175°C (350°F) for 50-65 minutes. The exact baking time will depend on your oven. To check for doneness, insert a toothpick or a thin knife into the center of the loaf. If it comes out clean or with a few moist crumbs attached, the banana bread is ready. If it comes out with wet batter, continue baking in 5-minute increments, checking each time.

Once baked, remove the loaf pan from the oven and let the banana bread cool in the pan for about 10-15 minutes. This allows it to set and makes it easier to remove.

Carefully invert the loaf pan to remove the banana bread onto a wire rack. Let it cool completely before slicing. Slicing while warm can cause it to crumble.