In a bowl, mix yogurt, lemon juice, garam masala, cumin, coriander, chili powder, and salt. Toss in the chicken pieces ensuring they are well-coated. Let it marinate for at least 15 minutes, preferably overnight for best flavor.

Heat 1 tablespoon of butter in a skillet over medium-high heat. Add the marinated chicken pieces and cook until browned. The chicken does not need to be fully cooked at this stage. Once browned, remove chicken and set aside.

In the same skillet, melt the remaining butter. Add chopped onion and sauté until golden. Add minced garlic and grated ginger, cooking for a minute or two. Stir in garam masala, cumin, paprika, turmeric, and chili powder, cooking until spices are fragrant, about 1 minute.

Pour in the tomato puree and season with salt, black pepper, and sugar. Let it simmer for about 10 minutes, stirring occasionally to prevent sticking.

After simmering, stir in the heavy cream until well combined. Return the browned chicken to the pan and let it simmer gently for 10-12 minutes until chicken is fully cooked and the sauce is creamy.

Sprinkle fresh cilantro on top and serve hot with naan, basmati rice, or cauliflower rice.