Topping: 1/3 cup sugar, 1 Tbs cinnamon, remaining stick of butter
Preheat oven to 350 F. Spray 9×5 loaf pan with nonstick spray, then coat with a dusting of flour.
Mix bananas, butter, sugar, egg, and vanilla together. Sprinkle baking soda and salt on top of the wet mixture. Then, gently stir in flour. Don’t over mix!
For the topping, mix the sugar and cinnamon together in a small dish and melt the remainder of the stick butter in a separate small dish.
Add the batter to the loaf pan, sprinkle half of the cinnamon/sugar mixture on top and swirl it in the batter. Sprinkle the remaining cinnamon/sugar mixture on top. Pour the melted butter on top of everything.
Bake for 50-60 minutes, but keep an eye on it. If you’re using muffin tins or another size pan, adjust accordingly.