The hype around San Marzanos, the sweet Italian plum tomatoes from Campania, has always been a bit of a mystery to me. Sweet, pulpy, low in acidity, and containing few seeds, they are said to be extraordinarily good for making sauces—and basically the only recognized name in the canned-tomato game. The long, meaty tomatoes are actually structurally distinct from most other plum tomatoes, containing only two seed pockets instead of the typical five. And in near mythical fashion, old Italian farmers grow them in the volcanic soil around Mount Vesuvius, which famously erupted in AD 79, leveling the Roman cities of Herculaneum and Pompeii in a vicious flood of molten lava.

Out of all that devastation comes the beauty of San Marzanos. It’s that volcanic soil and the microclimate—fanned with sea breezes from the Gulf of Naples—that accounts for their prized balanced flavor and tomato-iness. In Italy, tomatoes labeled as “San Marzano” must adhere to strict DOP (the Italian protected designation of origin) guidelines, which governs where they’re grown and how they’re processed. If you try growing the same seeds—“San Marzano” refers to both the plant and DOP—elsewhere, you just won’t get the same thing. The tomatoes are so revered in Italy that to make true Neapolitan pizza, according to the Associazione Verace Pizza Napoletana, you must use San Marzano tomatoes. Anything else will not do.