1. finely chop the red onion, peppers and garlic.
2. Fry the onion and peppers in a little olive oil on a medium heat for a few minutes.
3. Now add the garlic and continue to fry for 1 minute only, so that it doesn't burn.
4. Add the balsamic vingar and fry for 5 minutes.
5. Add the tin of tomatoes, chilli powder, sugar, and salt and pepper. Bring gently to the boil and then simmer for 10 minutes.
6. Leave to stand for a few minutes. Taste and add more seasoning, sugar or chilli as required.