Broiled grapefruit ambrosia

1. Heat the broiler.
2. With a sharp knife; cut the peel and membrane from the grapefruits and oranges.
3. Cut the fruit crosswise into ½-inch-thick slices.
4. In a shallow gratin baking dish or cast-iron skillet; alternately arrange the grapefruit and orange slices.
5. Sprinkle with brown sugar and dot with butter.
6. Broili the fruit until it is hot and lightly browned; about 5 minutes.
7. Sprinkle with coconut and broil just until the coconut is toasted.
8. Serve immediately.