- 1 untreated (about 12x10x1-inch) red cedar plank
- 3 tablespoons olive oil, divided
- 2 plum tomatoes, halved lengthwise
- 1 small sweet onion (such as Vidalia or Maui), quartered
- 1 large red bell pepper, halved lengthwise
- 1/2 cup Kalamata olives, pitted, coarsely chopped
- 3 anchovy fillets, finely chopped
- 2 garlic cloves, chopped
- 2 tablespoons chopped fresh basil
- 1 tablespoon drained capers
- 1 tablespoon white balsamic vinegar or unseasoned rice vinegar
- 4 6-ounce monkfish fillets
- 8 long thin slices prosciutto
- Fill roasting pan with water. Add cedar plank; weigh down with can or small pot to keep submerged and soak 1 day.
- Prepare barbecue (high heat). Brush grill rack with 1 tablespoon oil. Arrange tomatoes, onion, and bell pepper on rimmed baking sheet. Sprinkle with salt and pepper; drizzle with 1 tablespoon oil. Grill vegetables until lightly charred and blistered, turning occasionally with tongs, about 4 minutes for tomatoes and 8 minutes for onion and pepper. Return vegetables to same sheet and cool slightly.
- Peel tomato halves; peel pepper halves. Chop all vegetables coarsely and place in medium bowl. Add olives, anchovies, garlic, basil, capers, vinegar, and remaining 1 tablespoon oil. Toss to blend. Season relish to taste with salt and pepper. (Can be made 1 hour ahead. Let stand at room temperature.)
- Sprinkle fillets with salt and pepper. Wrap 2 prosciutto slices around each fillet, leaving top and bottom exposed. Secure prosciutto with toothpicks. Press each fillet slightly to flatten top.
- Drain cedar plank. Place fillets on plank. Spoon 1/4 cup relish atop each fillet and press to adhere. Place plank on grill; cover barbecue. Cook fish until just opaque in center and thermometer inserted into center registers 120°F, checking occasionally and spraying plank with water if beginning to burn, about 18 minutes. Transfer fish to plates. Serve, passing remaining relish.