Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9×5-inch loaf pan. In a large bowl, mash the bananas until smooth. Stir in the melted butter, sugar, eggs, and vanilla extract until well combined. In a separate bowl, whisk together the flour, baking soda, and salt. Add the dry ingredients to the wet ingredients and stir until just combined. Do not overmix, as this can make the banana bread tough. Pour the batter into the prepared loaf pan and bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out clean. Let cool in the pan for 10 minutes before removing to a wire rack to cool completely.