Heat olive oil in a heavy-bottomed pot over medium-high heat.
Season lamb with salt and pepper, then sear until browned on all sides.
Add onion, garlic, and ginger to the pot, sautéing until softened and fragrant.
Stir in ras el hanout and tomato paste, cooking for one minute to bloom the spices.
Pour in beef broth and add carrots, bringing the mixture to a gentle boil.
Reduce heat to low, cover, and simmer for 40 minutes until the lamb is fork-tender.
While the lamb simmers, cook pearl couscous in boiling water according to package directions.
Fluff the couscous with a fork, top with the lamb tagine, and garnish with fresh cilantro.