In a large skillet, heat a tablespoon of oil over high heat.Add the chicken and its marinade and sear, stirring, until golden brown or charred.Return to the bowl. In the same pan, sauté the chopped onion in 2 tablespoons of oil. Stir regularly until lightly browned.Add all the spices and cook for 2 minutes.Add the tomato paste and sugar and cook for about 10 minutes over medium heat.If you prefer a thicker sauce, you can blend it, but this is optional. Add the chicken pieces to this sauce along with the cream or coconut cream and mix. Season with salt and pepper. Simmer over low heat for about 30 minutes.
At the end of cooking, add the butter and stir.
Serve with rice, cheese naan, and chopped cilantro.