1. Cut tomatoes and onions into 4 or more pieces. Sprinkle with salt and leave overnight.
2. Next day pour off the liquid, put tomatoes and onion mixture into a pot with sugar and chillies.
3. Add enough vinegar to cover and bring to the boil.
Simmer for 1/2 hour.
4. Mix flour , curry powder, and mustard to a smooth paste witha little cold vinegar.
5. add to mixture and boil for 5 minutes. Pour into sterilised jars and seal tightly.