1.Preheat oven to 200°C/400°F.
2.Sprinkle chilli all over fish. Place each fish on a 30cm square of baking paper (parchment); top with lemon, drizzle with combined sauce and oil.
3.Gather corners of paper together; fold to enclose. Place parcels on oven tray; bake about 15 minutes.
4.Serve fish parcels sprinkled with onion.