This classic Roman dish, a.k.a. coda alla vaccinara, is as luscious as short ribs—and, thanks to Tony Mantuano’s recipe, just as easy to make. Just brown the oxtails, an affordable cut from the tail of a cow, then braise until tender.
Preheat oven to 325 degrees F. Set a roasting pan over medium heat. Peel and dice the carrot, onion, and half the celery (including leaves). Add oil to the roasting pan, followed by the vegetables and the pancetta. Cook, stirring, until vegetables are soft and pancetta begins to crisp up, 15 minutes.
Season oxtail with salt and pepper on both sides. Nestle into the roasting pan alongside the vegetables in an even layer to brown. Brown 5 minutes per side, then continue cooking another 5 minutes.
Remove oxtails to a platter. Add tomato paste to the roasting pan, and stir to deglaze, 1-2 minutes. Increase the heat to medium-high, add wine, and stir, making sure to scrape up all of the brown bits from the bottom, 1-2 minutes. Add tomato purée, cinnamon, and cocoa powder. Place oxtails back in the pan in a single layer. Braise in the oven, uncovered, 1½ hours. (Oxtails will be braised for a total of 2 hours or more.)
After 1½ hours, remove oxtails from oven. Slice remaining celery stalks (including leaves) into 3-inch-by-¼-inch strips. Add celery and marjoram. Turn oxtails over. Place back in the oven to braise for 30 minutes more.
Oxtails are done when the meat is fork tender. To serve, place oxtails on a large platter with the sauce and the celery. Serve immediately.