In a small bowl, mix the caramel sauce and rum until smooth. Cut each banana in half lengthwise but do not cut through the skin on the bottom. Open each banana slightly, like a book. Drizzle the caramel mixture evenly over the cut sides of each banana. Evenly space 4 raspberries inside each banana. Grill over Direct Medium heat until the bananas are warm and the skins are dark, 5 to 7 minutes, turning once. Peel the bananas and serve warm with ice cream, if desired.
Makes 4 servings