Preheat your oven to 350°F (175°C). Grease the loaf pan and line it with parchment paper for easy removal.
In a large mixing bowl, mash the bananas until smooth. Stir in the melted butter.
Add sugar, egg, and vanilla extract, mixing until well combined.
Sprinkle the baking soda and salt over the mixture and stir to incorporate.
Gently fold in the flour until just combined. If using add-ins, fold them in at this stage. Do not overmix.
Pour the batter into the prepared loaf pan and smooth the top.
Bake for 50-60 minutes, or until a toothpick inserted in the center comes out clean.
Let the bread cool in the pan for 10 minutes before transferring it to a cooling rack.