Step 1Preheat oven to 200 °C/ 400 °F (conventional), or 180 °C/ 355 °F (fan assisted).
Step 2Thinly slice half the lemon and set aside. Juice the other half and mix with the harissa, half of the olive oil, salt and half of the lemon juice to form a thin paste. Use half to baste the fish and set aside to marinate.