Cooking raw tuna may seem like a contradiction in terms, but the chemical reaction between the acid in the lemons and the flesh of the fish gives you the same texture and taste as though the tuna had been cooked with heat. Citrus-cooked tuna – or any other seafood done with this method – is called ceviche or seviche. Lemon-cooked tuna is tart, tangy and spicy; the perfect appetizer to accompany heavier winter soups and stews and a refreshing meal all its own when the weather’s hot.
Rinse your raw tuna in cool water and blot it dry with a paper towel.
Cut the tuna into small pieces, about the size of the tip of your thumb. The smaller the pieces, the faster the lemon juice will cook them. Place the tuna pieces in a glass bowl.
Cut six to eight lemons in half. Use a hand juicer to get the juice out of them. As you juice each one, pour the juice through a mesh strainer and into the tuna pieces.
Toss the tuna pieces in the lemon juice until they are thoroughly coated. You should see the change in color from pink to white starting.
Cover the bowl with plastic wrap and place it in the refrigerator. Leave it for at least one hour to make sure the tuna cooks through.