Heat 1 TBSP oil in a tagine or medium skillet (with a tight-fitting lid for later).
Add the tomato paste, garlic, tomatoes, and peppers. Sauté for about 3 minutes.
Add chickpeas, water, cilantro, salt, pepper, and ¼ tsp. Ras el hanout. Bring to a boil, reduce heat, cover and simmer for 30 minutes.
Meanwhile, mix the remaining Ras el hanout, paprika and cumin with 1 TBSP olive oil. Massage into both sides of the halibut and set aside.
After 30 minutes simmering, nestle the fish into the tomato mixture, squeeze with lemon juice and add lemon slices.
Cover and continue to cook for 5 minutes.
Fish is done when flakes with a fork. The cooking time will depend on the thickness of your fish.
Garnish with more cilantro and serve immediately with rice of choice, or couscous.