Marinate the chicken for at least 30 minutes with salt, cumin, coriander, and turmeric.
Heat the butter and oil in a large pan over medium heat.
Add the chopped onions, cooking until soft and golden brown.
Stir in the minced garlic and ginger, cooking for 1-2 minutes until fragrant.
Add the marinated chicken to the pan, cooking until it's fully browned on all sides.
Stir in the garam masala, ground cumin, and ground coriander, cooking for an additional minute.
Add the tomato paste, stirring to combine, and cook for 2-3 minutes until slightly caramelized.
Pour in the heavy cream, reduce the heat, and simmer for about 10 minutes.
Season with salt to taste and adjust other spices if necessary.
Garnish with chopped cilantro before serving.