1.Preheat oven to 220°C (200°C fan).
2.Boil, steam or microwave potatoes until just cooked; drain.
3.Meanwhile, seed tomatoes; slice into thin strips. Place half the onion and half the tomato in a large baking dish; top with chilli and half the basil, drizzle with 1 tablespoon of the oil.
4.Season fish; place on onion and tomato in large baking dish. Top with remaining onion, tomato and basil; add potatoes and drizzle with remaining oil.
5.Roast for 12 minutes or until fish is just cooked through.
To check if the fish is cooked, insert a knife into the thickest part of the flesh; the flesh should pierce easily with no resistance to the knife. The flesh will also have turned opaque.Note