Pat the oxtails dry with paper towels then season generously with salt.
Heat a large, deep braising pan or Dutch oven over medium-high heat. Pour in a few tablespoons of olive oil then add the oxtail.
Sear for a few minutes per side until browned all over. Remove from the pan and set aside.
In the same pan, add the chopped onion, carrot, celery and garlic and cook for 5-6 minutes until the vegetables start to soften and caramelize slightly.
Add the seasonings, tomatoes and beef stock. Season generously with salt and pepper. Add the browned oxtail back into the sauce then cover and place in the oven.
Allow the oxtail to braise slowly for 3-4 hours or until the meat falls off of the bone. Check on the liquid level half way through cooking and add more beef stock if necessary.
Once the beef is cooked, remove the pot from the oven. Remove the oxtail from the sauce with tongs then carefully shred the meat off the bones. Place the meat back into the sauce.
Return the pot to the stove and allow to simmer for another 10-15 minutes until the sauce is slightly reduced.
Taste and adjust seasoning if necessary.
Serve the ragu with pasta and plenty of freshly grated Parmesan cheese.