Melt the butter in a 10-inch heavy skillet over low heat. Add the brown sugar and nutmeg, and stir until the sugar dissolves. Add banana liqueur and bring sauce to simmer.
Add the bananas and cook for 1 minute on each side, carefully spooning sauce over bananas as they are cooking. Remove bananas from pan to a serving dish.
Carefully pour the bourbon into the pan and ignite with a long match or stick lighter. Continue to cook until the flames die out and the sauce coats the back of a spoon, 1 to 2 minutes. Serve immediately with ice cream, waffles, or crepes.