Add the lemon, yoghurt, turmeric, garlic, ginger and salt to the chicken. Marinade for 2 hours.
Heat your oil in a high-sided sauce pan. Add your cumin seeds then your onion. Fry until nicely browned. Tip in your marinated chicken. Fry for 2 mins. Add your spices and season with salt. Add your tomato puree. Cook out for a minute before adding the coconut milk then rice. Pop the lid on, turn the heat down low and cook for 20 minutes. Remove from the heat and allow to steam with the lid on for a further 10 minutes.