Heat the oil in a large heavy-based saucepan, add the onions and Garlic and cook for 10 minutes.
Add the Turmeric, Crushed Chillies, Medium Curry Powder, Ground Coriander and the tomato purée and cook for a further minute.
Add the diced lamb, water, tomatoes, lemon juice and Coriander.
Simmer for 15 minutes, then season to taste and serve with Pilau rice.