Atún de Almadraba Encebollado

Atún de almadraba encebollado belongs to Cádiz, on Andalucía's Atlantic coast: thick pieces of spring-run red tuna tucked beneath a great weight of onions, with bay, oregano, sweet pimentón, and dry white wine. There is no tomato and no thickened sauce. That would be another tuna stew. Here the onion becomes the sauce, glossy with olive oil and the juices of the fish.

The order decides the dish. Mark the tuna quickly and lift it out, then give the onions the time the fish cannot take. Cook them low until they collapse, turn dark gold, and taste properly sweet. Rush them and they stay wet and sharp; leave the tuna in while they cook and even a beautiful loin becomes dry. Return it only for the last two minutes, then take the pan off while the centre is still rosy.

Away from Cádiz, a traceable frozen Atlantic bluefin loin is the closest choice and often better handled than tired fish sold as fresh. Yellowfin loin is the honest substitute; it is leaner and a little less rich, so cut the final cooking by about thirty seconds. No hace falta haber pisado España. Weigh the onions, watch the tuna, and it comes out. Siempre sale, si lo sigues.