Slice aubergines and courgettes into 2.5cm pieces and chop peppers into bite-sized chunks.
Score tomatoes, soak in boiling water for one minute, peel, de-seed, and chop the flesh.
Sauté onions in olive oil in a casserole dish for 10 minutes until golden.
Add aubergines and courgettes to the pan and cook for 3 minutes over increased heat.
Stir in peppers, garlic, sugar, seasoning, and half the basil.
Cover and simmer over very gentle heat for 20 minutes.
Add tomatoes and cook for another 10 minutes.
Garnish with the remaining basil and serve.