Preheat your oven to 350°F (175°C).
In your mixing bowl, melt the butter in the microwave or on the stove. Let it cool slightly.
Add the very ripe bananas to the bowl with the melted butter. Mash the bananas until smooth.
Stir in the white sugar, then add the large egg and vanilla extract. Mix until smooth.
Sprinkle the all-purpose flour, baking soda, and salt over the wet mixture. Fold gently until just combined.
Grease your loaf pan or line it with parchment paper. Pour the batter into the pan and smooth the top.
Bake for 60-65 minutes or until a toothpick comes out clean. Cover with aluminum foil if the top browns too quickly.
Let the banana bread cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely before slicing.
