Peel and segment the orange, holding it over a bowl to catch the juices. Halve the segments. Mix them with the garlic, tomatoes, basil, olives and 4 tablespoons of the oil, season to taste with salt and pepper and set the salsa aside to infuse.
Wash and pat dry the fish and pull out any small bones with a pair of tweezers. Brush with the remaining oil and coat well with the jerk seasoning.
Heat a large heavy-based frying pan and fry the cod fillets, skin side down, for 5 minutes. Turn them over and cook for a further 3 minutes. Transfer to a low oven, 150°C (300°F), Gas Mark 2, to rest for about 5 minutes.
Serve the fish with the salsa and some rocket leaves.