What food does Carmy use to make tonnato sauce in Ribs?

Carmy uses canned tuna to make tonnato sauce in “Ribs.” The sauce becomes part of a lamb dish, pairing a rich, mayonnaise-like tuna preparation with the meat.

Tonnato is an Italian sauce whose name refers to tuna. A classic version is associated with vitello tonnato, a Piedmontese dish of chilled sliced veal covered with tuna sauce, often finished with capers, lemon and anchovies. The Bear adapts that tradition for a more contemporary restaurant plate.

The question can cause confusion because lamb is the protein served with the sauce, while anchovies may appear in some traditional tonnato recipes. They are not the ingredient Carmy identifies as the basis of this preparation. In the episode, the kitchen turns to canned tuna as a practical but sophisticated ingredient during a pressured service, showing how the chefs transform pantry food into fine-dining cuisine.