Bring 6 cups of water to a boil and add the oxtails. Reduce the heat to a simmer and let cook 10 minutes. Drain the oxtail, reserving the broth, and set the meat aside. Measure out 2 cups of the broth and discard the rest. Dissolve the tomato paste in the 2 cups of broth and set aside.

In a Dutch oven, heat the olive oil over high heat until smoking. Add the pancetta and saute until golden brown. Add the oxtails, 1 or 2 pieces at a time, and brown on all sides. Add the chopped carrots, half the parsley, onion and garlic and saute until vegetables are browned. Add the 1/2 cup white wine reduce the heat to a simmer. Cook, uncovered, until the wine is reduced by half. Add the remaining wine and season with salt and pepper, to taste. Pour the tomato paste-broth mixture over the meat. Cover and simmer for 2 hours.

After 2 hours, add the celery ribs and cook, covered, for 15 minutes more. Remove from heat. Make a salad with the chopped celery leaves, the remaining parsley, the chili flakes, cinnamon and salt and pepper to taste. Drizzle with extra virgin olive oil and lemon. Divide the oxtails evenly among 6 warmed pasta bowls and top with salad.