- To make garlic confit, heat oil and garlic in a saucepan over low heat. Cook on low heat for one hour. Do not brown the garlic. Add salt and pepper. Move to blender and mix (or mash by hand) into a chunky paste.
- Rub garlic confit over skin of fish. To intensify flavor, cover and refrigerate for 24 hours before cooking—but it can be cooked right away.
- Fire up grill to medium heat. Grill grapefruit halves face down for 15 minutes until dark brown so that the sugar of the grapefruit caramelizes. If the grill has a top shelf, leave the grapefruit on the top shelf face up to absorb some smoke.
- Add fish to grill. Squeeze one half grapefruit juice over fish.
- Grill over medium heat 6 minutes. Flip, squeeze remaining grapefruit half over fish, and cook an additional 5 minutes.
- Serve whole on platter. The meat should scoop out easily.