Preheat your oven to 350°F (175°C). Grease a 4x8-inch loaf pan.
In a mixing bowl, mash the bananas until smooth. Stir in melted butter.
Mix in baking soda and salt. Stir in sugar, beaten egg, and vanilla extract.
Add the flour and mix until just incorporated. Do not overmix.
Pour the batter into the prepared loaf pan and bake for 60-65 minutes, or until a toothpick inserted into the center comes out clean.
Let the banana bread cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.