Melt butter in a chafing dish or skillet.
Stir in sugar and heat until sugar melts.
Slice bananas lengthwise and add to butter sugar mixture; turn to coat on all sides.
Pour in rum and keep over medium heat.
Flame sauce by pouring a little rum into a teaspoon and holding it over flame of chafing dish or range until it flames; then use this flaming rum to light rum on top'of bananas.
Spoon flaming sauce over fruit several times.
Serve over vanilla or chocolate ice cream.