5 pounds oxtail, cut into 2-inch thick pieces
Kosher salt and freshly ground black pepper
6 tablespoons extra-virgin olive oil
Flour, for dredging
2 medium onions, sliced ¼-inch thick
4 cups red wine
2 cups brown chicken stock
2 cups basic tomato sauce
2 tablespoons fresh thyme leaves
Pecorino Romano, for grating
For the oxtail ragu:
Preheat the oven to 375 degrees F.
Trim the excess fat from the oxtails and season liberally with salt and pepper.
In a 6- to 8-quart heavy-bottomed casserole dish or Dutch oven, heat the olive oil over high heat until it is just smoking.
Quickly dredge the oxtails in the flour and sear them on all sides until browned, turning with long-handled tongs. This should take 8 to 10 minutes. Removed the browned oxtails to a plate and set aside.
Add the onions to the same pan and, stirring constantly with a wooden spoon, cook them until lightly browned, 5 to 7 minutes. Add the wine, stock, tomato sauce, and thyme and bring the mixture to a boil. Return the oxtails to the pot, submerging them in the liquid, and return the pot to a boil.
Cover the casserole and cook in the oven for 1 to 1 ½ hours, or until the meat is falling off the bone.
Remove the pan from the oven and carefully remove the oxtails with long-handled tongs. When they are cool enough to handle remove the meat from the bones and shred into small pieces with a fork. Discard the bones.
With a small ladle, skim the fat from the surface of the sauce. Return the shredded meat to the casserole. Place the casserole over medium-high heat, bring to a boil, then reduce to a simmer and allow to reduce to a very thick ragú.
Season with salt and pepper.