Preheat the oven to 350F. Place oven rack in lower middle position. Grease a 9x5 loaf pan. Set aside.
In a large mixing bowl, whisk the mashed banana and melted butter together until well-combined.
1 ½ cups mashed banana, ½ cup salted butter
Add the sugars, and mix in until combined.
¾ cup brown sugar, ⅓ cup granulated sugar
Stir in the egg, egg yolk, and vanilla extract until combined.
1 large egg, 1 large egg yolk, 1 ½ teaspoon vanilla extract
Add the flour, baking soda, salt, and cinnamon. Stir in just until combined.
2 cups sifted all-purpose flour, 1 ½ teaspoon baking soda, ½ teaspoon salt, ¾ teaspoon ground cinnamon
Pour the batter into the prepared pan.
Tent with foil around 25 minutes if browning too quickly.
Bake for about 55-70 minutes, or until a toothpick inserted in the center comes out clean.
Notes
Bananas: It’s important to use very ripe bananas. I like to use bananas that are equal parts brown spots and yellow.
Butter: This recipe uses melted butter. The butter shouldn’t be hot and sizzling. I melt it about 80% of the way and then whisk it to let it finish melted.
Brown sugar: Dark brown sugar or golden brown sugar will work.
Flour: It’s important to properly measure flour to avoid heavy or doughy banana bread. The proper way to measure flour is to stir it to break it up. Then lightly spoon it into a measuring cup and level it off.