Pat dry the oxtail and trim off any excess fat to your liking. Get a bowl of flour, season with salt, and dredge the meat in the flour until coated and shake off the excess.
In a dutch oven pot over medium heat, add some oil and sear the oxtail on all sides, until golden brown. Remove and set to the side.
In the same pot, add chopped leeks, celery, carrots, onion and garlic. Sautée for about 5 minutes until softened.
Add tomato paste and stir for another few minutes. Add some red wine, nestle the oxtail back inside the pot, and add beef stock until the meat is just covered.
Bring to a bubble, skim off any foam and discard, add some tied up herbs (I like using a bay leaf, fresh thyme and rosemary), then cover and place into the oven at 325 degrees for 3-4 hours, stirring every hour.
The meat will be super tender! Remove the herbs and serve with the braised veggies over some polenta with a side of asparagus. Option to blend up the braised veggies with the broth for a thicker sauce.