01 - Preheat your oven to 400°F for the initial high-heat roast.
02 - In a small bowl, combine ground cumin, smoked paprika, coriander powder, sea salt, black pepper, minced garlic, olive oil, and lemon zest. Mix thoroughly to form a paste.
03 - Pat the boneless leg of lamb completely dry with paper towels. Rub the spice paste evenly over the entire surface, pressing gently to adhere.
04 - Place the seasoned lamb in a roasting pan. Roast at 400°F for 40 minutes to develop a flavorful crust.
05 - Reduce oven temperature to 320°F and continue roasting for 45 to 60 minutes, until the internal temperature reaches 140°F for medium-rare doneness.
06 - Remove the lamb from the oven and tent loosely with aluminum foil. Allow to rest for 15 minutes so the juices redistribute.
07 - While the lamb rests, heat the tortillas in a dry skillet over medium heat for 30 seconds per side, or wrap in foil and warm in the oven for 5 minutes.
08 - Carve the rested lamb thinly against the grain to ensure tenderness.
09 - Layer each warm tortilla with shredded cabbage, sliced lamb, avocado, red onion, a dollop of Greek yogurt or sour cream, and fresh cilantro. Serve with lime wedges on the side.