Place the couscous, lemon rind and juice, salt and pepper in bowl and mix to combine. Pour in the water, stir and cover with cling film. Set aside until all the water has been absorbed and then stir in the spinach.
Make the Yoghurt and Garlic Dressing by simply stirring together all the ingredients. Season to taste. Set aside while you cook the fish.
Spread the harissa paste over the flesh side of the fish. Heat the oil in a frying pan over a medium heat. Then add the fish, skin-side down and cook for 4-5 minutes or until the skin is crispy.
Turn and cook for another 2-3 minutes until the fish flakes easily with a fork. Serve with the Couscous and Yoghurt and Garlic Dressing.