Preheat the oven to 350F. Grease an 8x4-inch loaf pan. Set aside.
In a large bowl, whisk mashed banana and melted butter together until well-combined.
Whisk in sugars until incorporated.
Add egg and vanilla, and whisk until well-combined.
Stir in flour, baking soda, salt, and cinnamon until combined.
Add nuts, and whisk until just incorporated.
Pour the batter into your prepared loaf pan, and sprinkle with additional nuts.
Bake for 40-60 minutes, or until a wooden toothpick inserted into the center comes out clean. I check the bread around 35 minutes and tent with foil if it is browning too quickly.
Let cool in pan for a 5-10 minutes.
Remove bread to wire cooling rack, and let cool completely before slicing.
Video
Notes
About 2 very ripe bananas, peeled
The butter should just barely be melted. I melt it about 80% of the way and then whisk it until its completely melted.
To properly measure the flour, stir it to break it up. Then lightly spoon it into the measuring up and level it off.
Be sure to finely chop the nuts if sprinkling them on top. If nuts aren't finely chopped, the weight can keep the bread from rising properly.