In a small bowl stir together the salt, cumin, black pepper, paprika and cinnamon. Season the oxtails all over with the spices. Heat a large Dutch oven or heavy bottomed saucepan over medium heat, add the oil and heat through.
Working in batches if needed, arrange the oxtails in a single layer in the pot. Sear the oxtails golden brown on all sides, about 6 minutes total. Transfer meat to a plate, repeating until all oxtails are browned.
Return the pot to medium heat, add the carrots, celery and onion and sauté, stirring occasionally until the vegetables are tender, about 6 minutes. Add the garlic and cook, stirring frequently, until fragrant, about 30 seconds.
Add the wine to the Dutch oven and simmer until it’s almost completely evaporated, about 8 to 10 minutes. Pour in the beef stock followed by the thyme and red pepper. Arrange the oxtails in the pot and bring to a simmer. Cover the pot and transfer to the oven.
Cook, turning oxtails half-way through cooking, until the meat is tender, about 3 hours. Remove the oxtails from the pot and let cool. Once cool, pull the oxtail meat from bones and shred the meat, discarding any large pieces of fat.
Add the meat back to the pot with the mustard greens and stir to combine, cooking over medium-low heat until the greens wilt, about an additional 10 minutes.
For the chile gremolata:
In a small mixing bowl, stir together Fresno peppers, cilantro, parsley, lime zest, lime juice, vinegar and olive oil until combined. Season with salt and set aside.
For assembly:
Place a large pot with salted water over medium heat and bring to a boil. Add the pasta and cook until just al dente, about 10 minutes. Drain the pasta, reserving about 1 cup of the pasta cooking water and return to the pot.
Ladle the oxtail stew over the pasta with the parmesan and ½ cup of the pasta cooking water, stirring to combine. Add the gremolata and stir once more. Divide among warmed pasta bowls. Serve immediately.