01 - Preheat the oven to 400°F.
02 - In a small bowl, mix cumin, paprika, coriander, salt, pepper, minced garlic, olive oil, and lemon zest to form a paste.
03 - Pat the lamb dry. Rub the spice paste all over the leg of lamb, ensuring even coverage.
04 - Place the lamb in a roasting pan and roast for 40 minutes.
05 - Reduce oven temperature to 320°F and continue roasting for 45–60 minutes, or until the internal temperature reaches 140°F for medium-rare.
06 - Remove the lamb from the oven, cover loosely with foil, and let rest for 15 minutes.
07 - Meanwhile, warm the tortillas in a dry skillet or wrap in foil and heat in the oven for 5 minutes.
08 - Thinly slice the rested lamb against the grain.
09 - To assemble each taco, layer with shredded cabbage, lamb slices, avocado, red onion, a dollop of yogurt or sour cream, and a sprinkle of cilantro. Serve with lime wedges.