1. Heat oil in frying pan, add onion, fry for 5-8 minutes until lightly browned. Stir in tomatoes, sugar, thyme and soy, bring to boil.
2. Simmer 5 mins, slip cod into sauce. Cover and gently cook for 8-10 mins until cod flakes easily. Serve with baked or steamed potatoes.
The sauce for this dish can be made up to a day ahead. Simply cool and chill until ready to reheat.