Charred Tuna Fish

• 1½ lb / 680–900 g tuna fish in a piece
• 2 tbsp sherry vinegar

Tuna fish is sometimes sold in a thick fillet, and sometimes cut across the bone into a steak. If the latter, this divides neatly into four by removing the central bone and cutting each of the two fillets in half. Cut the fish into even-sized pieces as thick as possible. Six thick chunks cooks far more satisfactorily than twelve neat slices. Brush the fish with the sherry vinegar and olive oil.