Make the chermoula by combining cilantro, garlic, cumin, paprika, 1 tsp salt, cayenne, saffron, 3 tbsp olive oil, and lemon juice. Reserve half the chermoula. Coat fish thoroughly with the other half, cover, and refrigerate at least 2 hours or overnight.

Add 1/3 cup olive oil to the base of a tagine or Dutch oven. Layer sliced onion across the bottom as a bed for the other ingredients.

Arrange carrot sticks over the onion, then layer potato slices on top. Season with ginger, 1/2 tsp salt, pepper, and turmeric.

Layer tomato slices over the potatoes. Distribute the reserved chermoula over the tomatoes.

Place the marinated fish on top with its marinade. Garnish with sliced peppers, lemon slices, and olives. Add 1/4 to 1/2 cup water.

Cover and cook over medium-low heat, allowing the tagine to slowly reach a simmer. Continue simmering for about 1 hour until fish and vegetables are cooked through and liquids reduce to a thick sauce. Add preserved lemon in the last few minutes, heat through, and serve.