Heat a little olive oil in a large soup pot over medium-high heat. Brown the oxtail pieces on all sides, then remove them from the pot and set aside.

In the same pot, add the onion, carrots, celery, and garlic. Sauté for 5–7 minutes until the vegetables start to soften. Stir in the tomato paste and cook briefly.

Pour in the red wine and let it reduce for a few minutes. Add the beef stock, bay leaf, thyme, rosemary, and the browned oxtail. Bring to a boil, then reduce the heat, cover, and let the soup gently simmer for about 3 hours.

Remove the oxtail from the soup, pull the meat off the bones, and return the meat to the pot. Season the soup with salt and pepper to taste.