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 for easy removal.
Step 2: In a large mixing bowl, mash the overripe bananas with a fork until mostly smooth but with a few small lumps remaining. The lumps add texture.
Step 3: Add the melted butter, granulated sugar, and brown sugar to the mashed bananas. Whisk until well combined. Stir in the eggs and vanilla extract until just incorporated.
Step 4: In a separate medium bowl, whisk together the all-purpose flour, baking soda, ground cinnamon (if using), and salt, ensuring no lumps.
Step 5: Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix the batter; a few streaks of flour are acceptable.
Step 6: Pour the batter into your prepared loaf pan. If desired, sprinkle the top with a little extra granulated sugar or chopped nuts.
Step 7: Bake for 55-65 minutes, or until a wooden skewer or toothpick inserted into the center comes out clean. If the top browns too quickly, loosely tent with foil.
Step 8: Remove the loaf from the oven and let it cool in the pan for 10-15 minutes before carefully transferring it to a wire rack to cool completely before slicing.