Add the chopped red onions to a blender with a small splash of water and blend until smooth. Set aside. Season the chicken pieces with salt and black pepper.
Heat oil in a large sauté pan over medium high heat. Add the chicken and stir fry for 3–4 minutes until cooked. Remove the chicken from the pan and set aside.
Add the ghee to the same pan. Pour in the onion purée and cook over medium heat, stirring regularly, until most of the moisture evaporates and the mixture begins to take on colour.
Stir in the tomato purée and curry powder. Add a small splash of water to loosen the sauce, cover, and cook for 5–7 minutes until thickened.
Return the chicken and any resting juices to the pan. Add a little more water if needed, bring to a gentle boil, reduce the heat, cover, and cook for 2 minutes.
Now you can add a bit more water, bring it up to a boil and lower the heat and cover and cook for 2 minutes.
Stir through the cilantro, taste, and adjust seasoning if needed. Serve hot.