- Heat the oven to 210°C/fan 190°C/gas mark 7. Slash the fish several times on each side.
- Mix the rosemary, olive oil - lemon zest and honey together. Rub into the fish and leave to marinate for 10 minutes.
- Place the fish in a roasting tin and season with salt and pepper. Bake in the oven for 10 minutes or until the fish is cooked - the flesh will turn white and flaky when it's done.
- Lift onto a bed of watercress and spoon any cooking juices over the top. Serve with lemon wedges.