How to Make It
Preheat the oven to 375°. In a small saucepan of boiling water, blanch the lemon zest until softened and pale, about 10 minutes. Drain and transfer to a small bowl. Stir in the lemon juice and honey.
In a small skillet, combine the coriander, cardamom, cumin, cinnamon, paprika, turmeric, and cayenne. Toast the spices over high heat, stirring frequently, until fragrant, about 1 minute.
Light a charcoal grill or heat a grill pan. Rub the lamb all over with the cut sides of the garlic. Coat well with the toasted spices. Season with salt and pepper and brush with the oil. Grill the lamb over moderate heat until well browned all over, about 5 minutes per side.
Transfer the leg of lamb to a roasting pan and roast in the oven for 1 1/4 hours. Brush the lamb liberally with the honey-lemon sauce and roast for about 15 minutes longer, or until an instant-read thermometer inserted in the thickest part of the leg registers 140° for medium-rare meat.
Transfer the lamb to a cutting board, cover loosely with foil and let rest for 15 minutes before carving. Pour the pan juices into a sauceboat and serve alongside the lamb.