Heat the oil in a large saucepan over a low heat. Add the onion and fry for 10–12 minutes until soft and translucent. Add the courgettes and cook for a further 5–6 minutes, stirring occasionally.
Add the tomatoes (including the juices) and garlic, and continue to cook over a medium heat for 20 minutes.
Stir in the chilli powder, turmeric and dried mint, and cook for a few more minutes to allow the flavours to mingle. Season to taste and serve with couscous or steamed white rice.