Chefs all over the world swear by San Marzano tomatoes for anything that requires the canned nightshade: pizza, soup, sauce. Grown in the shadow of Mt. Vesuvius by farmers who've been doing so for decades, San Marzano tomatoes are prized for their particular meatiness, oblong shape, and low seed count. In Italy, they have to abide by strict DOP—or protected designation of origin—guidelines, which govern everything from how and where you can grow them, how they're harvested, and how they're processed. Only tomatoes grown in Agro Sarnese-Nocerino, close to Naples, can be considered San Marzano tomatoes. However, that doesn't stop fake San Marzano tomatoes from appearing on American grocery store shelves. 

San Marzano tomatoes may well be the best canned tomatoes in the world, but it's unlikely that you've ever picked up the real ones at your local store. I know, I've been duped, too. According to Gustiamo, a small Italian importing company, the consortium that oversees certification for the product says that 95 percent of San Marzano tomatoes in the US are fake. In an investigation at the website Taste, Mari Uyehara found out that unlabeled cans will be shipped to the US, only to have people put a phony DOP label on them. It's perfectly legal in the United States for people to use the name San Marzano as a brand name, so that happens frequently, too. 

Fortunately, there are a few ways to avoid buying cans of fake San Marzano tomatoes. The authentic tomatoes never appear crushed or diced. You should expect to pay more than usual for a can of the real tomatoes; the price will be closer to $5 than $1. Keep an eye out for DOP seals, too, but be wary. More than anything, know that the real deal is labeled as “Pomodoro S. Marzano dell’Agro Sarnese-Nocerino.” 

If you want to make things easier: Just as many chefs think Muir Glen California tomatoes will treat you well. And you can find those on any supermarket shelf.