Roast Tuna with Onions and Lemon

A useful technique for any dark-fleshed fish, including whole mackerel or bluefish (which may be stuffed with the onion mixture), steaks of Spanish mackerel, or fillets of pompano; adjust the cooking time accordingly.

I really like pasta before this—something quite simple, like Pasta with Pepper and Cheese or Pasta with Broccoli Raab.