Toss lamb with 1 ½ tablespoons ras el hanout and 2 ½ teaspoons salt in a medium bowl until evenly coated. Let stand at room temperature 1 hour, or cover and chill up to 2 days.

Grate 1 onion half on largest holes of a box grater; set aside remaining half. Place grated onion in a clean dish towel or piece of cheesecloth, and squeeze over sink to remove as much liquid as possible. Stir together lamb and grated onion in base of a 2-quart tagine. Cover and cook on a gas stovetop or a diffuser over an electric range over very low until lamb is cooked through but not yet tender and juices are pooling in tagine, about 1 hour and 30 minutes.

Thinly slice remaining onion half. Add sliced onion to tagine; stir to combine. Cover and continue cooking on stovetop until lamb is tender, about 1 hour.

Preheat oven to 300°F with oven rack in upper third of oven. Toss together butternut squash, honey, remaining 2 teaspoons ras el hanout, and remaining 1 teaspoon salt in a medium bowl. Add butternut squash mixture and apricots to tagine; stir to combine, making sure apricots are submerged in pan juices. Transfer tagine, uncovered, to upper third of preheated oven. Increase oven temperature to 425°F. Bake until squash is tender, about 30 minutes.

Remove tagine from oven, and sprinkle with olives, pine nuts, and cilantro. Cover and let stand 5 minutes. Garnish with mint leaves, and serve with couscous.