Full disclaimer: Carbonara is a no more deserving subject for this article than amatriciana or cacio e pepe, both of which you should absolutely order in Rome (do Da Francesco for amatriciana, and Flavio Valevodetto for cacio e pepe). But carbonara's popularity Stateside—plus an American-slanted back story—makes it the one dish you never want to miss. That, and the fact that it is pretty much the perfect plate of comfort food.
Local lore suggests that this dish, comprised of just guanciale, pecorino, egg, pasta and pepper, was concocted during the Allied occupation of Italy post-World War Two. The U.S. servicemen were hungry for the bacon and eggs they were raised on back home, and a local restaurant had the sense to combine those ingredients, mix them with hot pasta, and finish it all with a few cracks of pepper, to please the troops' homesick tastebuds. Though the restaurant that created the dish has never been confirmed, we've heard it was 90-year-old Al Moro by the Trevi Fountain, whose own version is as light and silky as any you'd expect to come from the dish's birthplace. And bonus, unlike fettuccine Alfredo, you don't have to rely solely on one or two restaurants around town to get your fix. Every trattoria does a version, though you are going to want one that follows the three cardinal rules of something nonna would eat: The meat should be guanciale, not pancetta; flavorful add-ins like garlic, mushrooms or onions are a strict no; and if the "chef" has thickened the sauce with cream, just put down your fork and walk out.
Plenty of places around town get it right, but there are a few we return to every time we are back in town. Roscioli is located in that tangle of alleys behind Campo dei Fiori and is famous for stiff silver service, a two-month-long wait list, and using specialty eggs from Tuscan chickens fed on a goat-milk diet by, erm, celebrated egg enthusiast Paolo Parisi up in Livorno. A more classic take (read: good ol' fashioned Roman eggs, spaghetti instead of rigatoni, a mound of fresh pecorino on top) and can be found at Armando al Pantheon, the only restaurant in all of Rome within full view of a major monument that we give full permission to eat at (and if you are tempted to make a last minute switch to its signature fettuccine with chicken gizzards instead, we'd forgive you).
The truest version, however, will always be found in either of our two favorite neighborhoods to dine out in. At Piperno in the Jewish quarter, found in the shadows of the 2,000-year-old Porto d'Ottavia, the balance of creamy egg and salty, chewy chunks of guanciale may make its carbonara Rome's ultimate, no-shame comfort dish. While farther south in the no frills neighborhood of Testaccio, any number of osterie that line the vibrant Via del Monte Testaccio serve excellent, honest plates of carbonara using hand made fettuccine and the city's greatest guanciale cuts from famed local delis like Volpetti—we head to the wooden tables at Perilli for the simple trattoria's sauce, which is gently mixed into a yellowy silk from the yolk. But the good news about doing dinner on the fly in Testaccio is that you can't eat badly; having managed to stay off the tourist radar, you'll share the dining room with Romans and an Italian-only-speaking waitstaff. So, if Perilli is full, just go next door.