Heat the extra virgin olive oil in a heavy-bottomed pot or ceramic tagine over medium-high heat.
Season the cubed lamb leg with sea salt and black pepper, then sear in the pot until a golden-brown crust forms on all sides.
Add the diced yellow onion, sliced carrots, and zucchini to the pot, sautéing for 5-6 minutes until the vegetables begin to soften.
Stir in the minced garlic, grated ginger, and Ras el Hanout, stirring constantly for 60 seconds to release the fragrant oils from the spices.
Pour in the beef bone broth and add the rinsed chickpeas and the chopped Medjool date.
Bring the liquid to a gentle boil, then immediately reduce the heat to low, cover tightly, and simmer for 40 minutes until the lamb is fork-tender.
While the tagine finishes, place the dry couscous in a small heat-proof bowl, cover with an equal amount of boiling water, and let sit for 5 minutes.
Fluff the couscous with a fork and serve the warm tagine over the grains, finishing with fresh cilantro and a squeeze of lemon juice.