In a large, deep skillet, heat 2 tablespoons of the oil. Add half of the onion and cook over moderate heat, stirring, until browned, 8 minutes. With a slotted spoon, transfer to a plate. Add the raisins and cashews to the skillet and cook for 1 minute. Transfer to the plate.
Add the remaining 2 tablespoons of oil to the skillet along with the remaining onion and both peppers. Cook until softened, about 7 minutes. Add the tomatoes, ras el hanout and stock, cover and cook over low heat for 10 minutes. Season the fish with salt and pepper and add to the skillet. Cook over moderately high heat until the fish is cooked, 5 minutes.
Bring 2 cups of water to a boil. Put the couscous in a heatproof bowl and toss with the cinnamon and cumin. Pour the boiling water over the couscous, cover and let stand for 10 minutes. Stir in the butter and season with salt and pepper. Spoon the couscous into bowls and top with the fish stew. Garnish with the onion, raisins, cashews and scallions.
Bright, tropical California Chardonnay.