Heat the oil in a heavy bottomed pan or karahi.
Add the onion and cook on a gentle heat, stirring often, until the onions are a deep golden colour.
Add the garlic and ginger to the pan and cook for 30 seconds.
Add the Bhuna Masala and cook again for 30 seconds, stirring so the spices don’t catch. Add a splash of water if the spices start to stick.
Add the diluted tomato puree and let reduce to a thick paste
Add the chicken to the pan and stir to coat with the sauce.
Add the hotel gravy to the pan and bring to the simmer. Cook for around 15 minutes.
Add the tomatoes, chillies, lemon juice and salt. Cook for a further 8 minutes, or until the chicken is cooked through.
Check for seasoning and add more salt if needed, add the coriander, and stir through.
Serve the curry with rice and Indian bread such as chapatti.