Preheat the broiler. Using a paring knife, cut between the membranes of the grapefruit.
Cut a small piece off the bottom of each grapefruit half so that it sits flat.
Drizzle 2 teaspoons syrup on each half, then sprinkle each with 1/4 teaspoon of sugar and 1/2 teaspoon of butter.
Broil 2 inches from the heat source for 8 minutes, or until golden brown. Serve hot. Serves 2.