Grease the bottom and sides of a loaf pan with butter and then sprinkle with 1 tbsp of sugar. Shake the pan pan to distribute the sugar around the bottom and up the sides. Set aside.
In a medium bowl, combine flour, baking powder, baking soda, cinnamon and salt. Make a well in the center of the mixture and set aside.
In another bowl, combine the egg, bananas, sugar and oil. Add all at once to the dry mixture.
Stir until moistened (it will still be lumpy)
Pour half of the batter into the pan. Drop spoonfuls of Nutella on top of the batter and using a knife or skewer, draw it through the batter to create swirls.
Cover with the other half of the batter and drop the remaining Nutella by spoonful on top. Once again, draw a knife through the spread to swirl the chocolate spread and the batter together.
Bake at 350° for 50-55 minutes, or until a toothpick inserted in the center comes out nearly clean. Allow to cool completely before removing from the pan.
Notes
Adapted from Better Homes and Garden New Cookbook, 11th ed.