Preheat the oven to 350°F (175°C). Grease a 9×5 inch loaf pan with butter or non-stick spray.
In a large mixing bowl, combine the mashed bananas with the melted butter and mix well.
Add the granulated sugar, beaten egg, and vanilla extract to the banana mixture and stir until combined.
Sprinkle the baking soda, salt, and ground cinnamon over the mixture and mix in.
Add the all-purpose flour and gently fold it into the wet ingredients until just combined. Do not overmix.
Pour the batter into the prepared loaf pan and spread it evenly.
Bake in the preheated oven for 60 minutes, or until a toothpick inserted into the center comes out clean.
Remove the banana bread from the oven and let it cool in the pan for 10 minutes.
Transfer the bread to a wire rack to cool completely before slicing and serving.