Combine the lemon zest, cumin, coriander, pepper, paprika and salt in a small bowl, mixing well. Set aside 3 tablespoons of the spice mix for the couscous. With the remaining, gently rub the spice onto both sides of the fish and allow them to sit for 15 minutes.
Meanwhile, prepare the couscous. In a large bowl, combine the couscous and water. Allow this to sit for 5 minutes or until all the liquid has been absorbed, then gently fluff with a fork. Add the remaining ingredients and combine well. Set aside, covered, while the fish is cooking.
Heat a non-stick frying pan over a medium heat, add the oil and cook the fish for 2-3 minutes on each side or until the fish flakes easily when tested with a fork.
To serve, place a mound of couscous onto each plate and top with a fish steak. Serve with a lemon wedge to squeeze over the fish.
Tip: This is a mildly spiced dish. If you like, you can substitute 1 teaspoon of the mild paprika for some chili powder for a hotter dish.
Per serving: 552 calories, 23 g fat (7.5 g saturated), 48 g protein, 36 g carbohydrate, 7.5 g fibre