Preheat oven to 325 degrees.

On a stove, heat a large cast iron pot on medium-high, once hot, reduce heat and add 1/2 of the olive oil. Add onions and sauté until translucent, season with salt and pepper.

Add in carrots and celery, and cook until tender. Once tender, add in tomato paste and coat vegetables well. Sprinkle in garlic, and allow to cook until aromatic. Remove from pot and set aside.

In the same pot, add oxtails and tomatoes. Deglaze pan with dry red wine or red wine vinegar, so that all of the crunchy bits on the bottom lift off the pot.

Add Sea salt and freshly ground black pepper to taste. Once deglazed, add mixture which was set aside and half of low- sodium beef bone broth, bay leaves, thyme, and lemon zest.

Place cast iron pot in the oven, with a lid on, and allow to cook until oxtails are fork tender. Check on the oxtail periodically and if the liquid is too low, reduce heat, and add more bone broth.

Serve oxtail with mashed cauliflower.