Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius) and grease a 4x8 inch loaf pan with butter or non-stick spray.

In a large mixing bowl, mash the bananas with a fork or whisk until a smooth consistency is achieved.

Incorporate the melted butter into the mashed bananas using a spatula.

Add the granulated sugar, beaten egg, and vanilla extract; stir until the mixture is homogeneous.

Sprinkle the baking soda and salt evenly over the wet mixture and stir to distribute.

Fold in the all-purpose flour gradually, stirring only until no dry streaks remain to avoid gluten over-development.

Transfer the batter into the prepared loaf pan and level the surface with a spatula.

Bake for 60 minutes, or until a wooden skewer inserted into the center of the loaf emerges clean.

Remove from oven and allow the bread to cool in the pan for 10 minutes before transferring to a wire rack for final cooling.