Melt butter and brown sugar in a frying pan.
Chop one banana and add to the pan. Sauté over medium heat until lightly browned, turning once.
Sprinkle with cinnamon. Remove pan from heat.
Add rum and flambé by carefully lighting the sauce on fire with a long-reach lighter. Spoon flaming sauce over the banana pieces until flame is extinguished and serve with vanilla ice cream or on top of a simple cake.