Every summer, bluefin tuna migrate through the Mediterranean Sea. To make the most of this brief window, seafood chefs on the Italian island of Sardinia use every part of the animal they call tonno rosso, including its heart. 

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.

For those who seek larger portions of tuna heart, many restaurants also serve it sliced, with lemon and olive oil.