I don't entertain often, but when I do I want to be SURE everything turns out right, so I skip the complicated stuff and use my go-tos, of which this is one. Elegant and tasty enough for company, but sooo easy and absolutely foolproof!
Melt butter in a chafing dish or skillet. Stir in sugar and heat over medium heat until sugar melts.
Halve, then slice bananas lengthwise and add to butter-sugar mixture; turn to coat all sides. Pour in rum, keeping on medium heat.
Pour a little rum into a teaspoon, hold it over the flame of chafing dish, gas range, or other fire source until it flames. Use the flaming rum to light rum in skillet. Spoon flaming sauce over bananas several times. When flames die down, serve with vanilla (or other) ice cream.