Preheat the oven to 350°F. Spray a 8- by 4- by 2 ½ inch loaf pan with non-stick cooking spray.
In a large mixing bowl, using a fork, whisk the egg. Add the mashed bananas, flour, sugar, milk, butter, baking powder and salt, mixing well until combined.
Pour the batter into the prepared loaf pan. Bake for 45 to 55 minutes or until a tester inserted into the center comes out clean.
Transfer pan to a cooling rack and let stand 10 minutes. Invert a plate on top of the banana bread and flip the plate and pan upside down. Tap pan gently to remove bread. Turn bread upright and let cool completely. Slice and serve.
Banana skins should have larger dark patches for best results.Use a fork to mash the bananas until smooth.If using salted butter, decrease salt to a pinch.