Tamari is a type of soy sauce that appeals to people with specific dietary restrictions. Unlike conventional soy sauce, it doesn’t contain wheat and is therefore gluten-free. It also tends to be higher in protein, and organic versions generally don’t contain monosodium glutamate (MSG).

Tamari is also usually milder in flavor and tends to be thicker than other soy sauces.

Tamari has long been available in health-food stores, but with the rise of popularity in East Asian flavors and the growth in the number of people avoiding gluten, it has become more mainstream over the past couple of decades. The increased interest in protein — despite the fact that most Americans actually consume more protein than they need — has also sparked interest in tamari.

Market research firm Datassential reports that tamari is currently found on 1.4% of menus in the United States, up by 19% over the past four years.

Click through the gallery to learn more about this week’s Flavor of the Week and see how one restaurant is using tamari on the menu.