Chop your vegetables into 2 cm cubes roughly. I use a vegetable chopper machine. Oh my days it blows my mind how easy it makes the whole chopping game. Otherwise chop carefully with a sharp knife.
Add the onions and aubergine to a large frying pan with a splash of olive oil (2tsp) or similar flavourless oil.
Fry uncovered over a medium heat for 5 minutes, stirring every minute or so.
Add the chopped courgettes and stir through.
Cover and fry over a medium heat for another 5 minutes. Stir every now and again to stop any vegetables sticking to the bottom.
Add the 2 chopped peppers.
Stir through, cover and cook again for another 5 minutes. Stir once every minute just so it doesn't catch on the bottom.
Add the tin of tomatoes, tomato puree, garlic, basil, sugar and balsamic vinegar.
Stir through and cook uncovered at a gentle simmer for 25 minutes. The liquid will have evaporated and the mixture started to become a bit jammy and melded altogether.
Serve straight away or allow to cool and refrigerate if making ahead.