This recipe is a real tribute to Persian cuisine. The dried lime peel in the Isphahan N.1 spice blend has an intense, sweet-citrusy flavor that enhances both the couscous and the quick marinade for fish.
Marinate the fish: In a bowl, whisk together 2 tablespoons of the Isphahan spice blend, 2 tablespoons of olive oil, and the lemon zest. Place the marinade and the fish in a large, resealable plastic bag or baking dish and refrigerate for 30 minutes.
Using a sharp knife, cut the peel and white pith from the lemon and orange. Working over a bowl, cut between the membranes to release the citrus segments. Discard any seeds and cut the citrus segments into 1/8 inch pieces. Squeeze the remaining juice into the bowl. Add 1 tablespoon of olive oil, season with salt and pepper and set aside.
Preheat the oven to 350°F and line a rimmed baking sheet with parchment paper.
In a large skillet, heat 2 tablespoons of olive oil over medium-low heat. Add the onion, season with salt and pepper, and cook until the onion becomes translucent, about 5 minutes. Add the bell peppers and fennel and cook until the vegetables are soft, about 10 to 15 minutes.
Meanwhile, in a medium saucepan, bring the vegetable stock to a simmer and add the remaining 1 1/2 teaspoons of Isphahan and the turmeric; season with salt and pepper. Once the vegetables are ready, add the simmering stock and couscous. Stir and turn off the heat. Cover with a lid and set aside for 5 minutes, then gently fluff the couscous with a fork and stir in the orange zest. Season to taste with salt and pepper.
Season both sides of the fish with salt and pepper and place on the baking sheet, skin side down. Bake the fish until cooked through, about 5 to 8 minutes.
Divide the couscous among four plates and top each with a piece of fish. Spoon some of the citrus dressing over the fish and serve.
