Mix together the sugar, cinnamon and ginger in a small bowl.
Position an oven rack so that it sits 4 inches below the broiler. Preheat the oven to broil.
Put the grapefruit cut-side up on a baking sheet. Divide the sugar mixture over the top of each and place under the broiler. Broil until lightly golden brown, about 3 minutes.
Recipe courtesy of Bobby Flay