Preheat your oven to 160°C fan (180°C conventional / 350°F / gas mark 4).
Using an oven proof pan, fry the onion and garlic in the oil for 5 minutes until the onion is soft and translucent.
1 tbsp olive oil, 1 onion, 2 cloves garlic
Add the other vegetables (except the tomatoes) and fry for another 5 minutes, stirring a couple of times to ensure an even cook.
1 red bell pepper, 1 aubergine, 1 courgette
Add the rest of the ingredients, stir together, cover the pan with a lid and cook in the oven at 160°C for 3 hours, stirring once or twice during this time.
2 tomatoes, 400 g tinned chopped tomatoes, 2 tbsp tomato puree, 1 tbsp balsamic vinegar, 100 ml vegetable stock, 1 tbsp fresh basil, 2 sprigs thyme