Method

1. Cut 12 lemon slices, reserving the remaining fruit.
2. Rinse the monkfish fillets under cold running water and pat dry with paper towels.
3. Place the monkfish fillets, cut-side up, on a work surface and divide the citrus slices among them.
4. Top with the lemon thyme. Tie each fillet at intervals with kitchen string to secure the citrus slices and thyme.
5. Place the monkfish in a large, shallow, nonmetallic dish.
6. Squeeze the juice from the remaining fruit into a pitcher, add the oil, and mix together.
7. Season to taste with salt, then spoon the mixture over the fish. Cover with plastic wrap and let marinate in the refrigerator for up to 1 hour, spooning the marinade over the fish tails once or twice. Preheat the broiler.
8. Drain the fish, reserving the marinade.
9. Sprinkle the crushed peppercorns over the fish, pressing them in with your fingers, then cook over medium high heat, turning and brushing frequently with the marinade, for 20-25 minutes. Transfer to a cutting board, remove and discard the string, and cut the fish into slices.
10. Serve immediately.