How do I cook a tuna steak rare in the middle?

Tuna is the one common fish that is genuinely ruined by cooking it through. Its muscle is dense, dark and very lean, so where a cooked salmon fillet stays succulent, a cooked-through tuna steak becomes dry and grainy in the way an overcooked beef fillet does. The whole technique is a hard fast crust and a cold centre.

Safety

What you'll need

• A thick tuna steak, at least 2.5cm
• A heavy pan or ridged griddle
• A high smoke point oil

Step by step

1. Buy a steak thick enough to have a middle.At least 2.5cm, ideally 3 to 4cm. A thin steak has no rare centre available — by the time both faces have colour, the whole thing is cooked. If the counter only has thin steaks, cook them through and accept it, or buy something else.
2. Look at the colour and judge the fish.Fresh tuna is deep red to dark pink and translucent, with a firm springy feel. Brown or dull patches mean age. An unnaturally uniform bright cherry red can mean it has been treated with carbon monoxide to fix the colour, which preserves the look long after the fish has aged.
3. Bring it to room temperature for fifteen minutes and dry it.A fridge-cold steak needs longer in the pan, which is exactly what you are trying to avoid. Pat it thoroughly dry on both faces and the edges.
4. Season heavily just before it goes in.Salt and coarse pepper, or a crust of sesame seeds, crushed peppercorns or dried herbs pressed onto both faces. There is very little cooking time in which to develop flavour, so the surface has to carry it.
5. Oil the fish, not the pan.Rub a thin film over the steak. Oil poured into a smoking pan burns and smokes before the fish arrives.
6. Get the pan properly hot before it goes near the fish.Heavy cast iron or a ridged griddle over high heat until it is just beginning to smoke. A moderate pan cooks the steak through slowly, which is the failure mode.
7. Sear 60 to 90 seconds a side and no more.Press it flat for the first few seconds for full contact. You are looking for a browned band about 3mm deep on each face and a raw red centre. Sear the edges briefly too by holding the steak on its side with tongs.
8. Rest it briefly and slice against the grain.Two minutes on a warm plate, then slice across the muscle fibres about 1cm thick. Sliced with the grain it eats stringy, exactly as beef does.

Tips

• Frozen-at-sea tuna loins are usually better than the counter steaks and are the safer choice for eating rare, because commercial freezing kills parasites.
• A soy, ginger and sesame marinade for twenty minutes is worth it — but pat the steak dry before searing or it will steam instead of crusting.
• If you are nervous about a raw centre, cook it to medium and stop there. Medium is still good. Well done is not, and no sauce recovers it.
• Yellowfin and albacore are the tuna most often sold as steaks in the UK. Bluefin is expensive and under real stock pressure; check the Good Fish Guide before buying it.
• Leftover seared tuna is excellent cold, sliced thin into a salad. It is one of the few cooked fish that is genuinely better cold than reheated.

Common mistakes

• Cooking a tuna steak like a salmon fillet — Salmon has fat running through it and stays moist at doneness; tuna has almost none and goes dry and grainy at the same point. The timings are completely different and the salmon timing ruins the tuna.
• Using a thin steak and expecting a rare middle — There is not enough thickness for a temperature gradient. Two 90-second sears on a 1.5cm steak cooks it right through and there is nothing you can do about it once it is in the pan.
• Slicing along the grain — Tuna muscle fibre is coarse and runs in long bundles. Cut the wrong way it is stringy and chewy even when perfectly cooked.

If it doesn't work

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