Use a sharp knife to make some slits in the shoulder. Prepare the marinade in a large bowl. Mix the salt, black pepper, cumin, turmeric, vinegar, olive oil, and lemon juice thoroughly.

Brush the marinate all over the cut of lamb, back and front. Allow it to marinade in the refrigerator for a minimum of two hours but up to twelve hours. Bring the lamb fully to room temperature before roasting.

Preheat the oven to 400 degrees F. Lay out a few pieces of foil large enough to wrap around the lamb shoulder and top it with a few pieces of parchment paper.

Spread the chopped onion, carrots, sliced garlic, cinnamon sticks, whole cloves, coriander seeds, and cardamom pods on the foil and parchment. Place the marinated lamb shoulder fat side up on the paper, wrap well with the paper, and then close it with the foil.

Fit a cooling rack inside a roasting pan, add three cups of water on the bottom, and place the lamb inside. Cook for 30 minutes at 400 degrees F. Lower the oven temperature to 275 degrees F and continue to cook for another six and a half hours.

Uncover the lamb. Drain the juices into a clear measuring cup and pour it back on top of the lamb. Continue to allow the lamb to brown for another fifteen minutes. Remove the slow-roasted lamb from the oven and allow it to rest for 20 minutes. Serve the lamb hot with its juices on the side, and enjoy!