Cut bananas in half lengthwise; set aside.
In skillet or chafing dish, melt butter over medium heat; stir in sugar until melted. Add bananas, cut side down; cook, turning once, for about 5 minutes or until just barely tender. Sprinkle with cinnamon and nutmeg.
Pour rum, and banana liqueur (if using), over bananas, shaking pan to distribute liquid. Averting face, ignite with long wooden match. Using long handled spoon baste bananas with flaming sauce until the flames subside.
Serve immediately with ice cream.