Step 1: Prepare the Lamb Shanks

1. Pat the lamb shanks dry with paper towels and season generously with salt and pepper.
2. In a large Dutch oven or heavy pot, heat olive oil over medium-high heat. Sear the lamb shanks on all sides until browned (about 4-5 minutes per side). Remove and set aside.

Step 2: Sauté the Vegetables

1. In the same pot, add chopped onion, carrots, and celery. Sauté for about 5-7 minutes until softened.
2. Stir in minced garlic and cook for another minute until fragrant.

Step 3: Deglaze the Pot

1. Pour in the red wine, scraping up any browned bits from the bottom of the pot.
2. Bring to a simmer and let it reduce by half (about 5-10 minutes).

Step 4: Braise the Lamb

1. Return the lamb shanks to the pot. Add the broth, diced tomatoes, tomato paste, rosemary, thyme, and bay leaf. Bring to a simmer.
2. Cover the pot with a lid and transfer to a preheated oven at 325°F (160°C). Braise for 2-3 hours, or until the lamb is fork-tender.

Step 5: Finish and Serve

1. Carefully remove the pot from the oven and discard the bay leaf.
2. Let the lamb shanks rest for a few minutes before serving.
3. Serve the lamb shanks with the braising liquid spooned over the top. Garnish with fresh parsley and lemon zest if desired.