In the same pot, fry the onion and garlic until soft. Add the tomatoes, bay leaves and thyme. Simmer for 5 min, then return the oxtail to the pot.
Add the beef stock and simmer for 3 – 4 hours, or until the oxtail is cooked and tender. Check every 30 min to ensure it does not dry out. Add more stock or water if necessary. In the