Remove the fish from the marinade, setting the marinade aside. Drain the fish well. Season with salt and pepper. In an ovenproof non-stick pan, brown one side of the fillets in the oil, 2 to 3 minutes. Turn the fillets and deglaze with the marinade. Sprinkle the prosciutto on the fillets and top with the orange slices. Bake for about 10 minutes. Serve with steamed rice and a colourful salad.