To prepare cuore di tonno, Sardinians salt and press the heart under weights for twenty days, then leave it to air-dry.

After the curing process, the organ will be rock hard and extremely briny. Its ocean-heavy odor might even recall the bilge of a ship.

Cuore di tonno packs a flavorful punch. Just a few shavings will add a salty, savory, ferric tang to soups, sauces, and pasta dishes. The grated heart has a texture reminiscent of another shaved-fish topping: Japanese bonito flakes.