Heat 3 tablespoons of the oil in a saucepan and add the onion and garlic. Fry for 6-7 minutes till the onion is lightly browned.
In a small bowl, mix the tomato puree with the remaining oil, cumin, coriander, turmeric, chili powder, garam masala and salt to form a thick paste. Tip the paste into the onion mixture and fry for half a minute.
Stir in the turkey pieces and cook for 1 minute.
Add 1 1/2 cups of hot water from the kettle and simmer for 3-4 minutes. Mix in the ginger (if using) and the lemon juice.
Garnish with cilantro and serve with plain basmati rice, bread and a salad of crisp lettuce.