In a large bowl, combine yogurt, garlic, ginger, salt, cumin, garam masala, chili powder, and lemon juice. Mix well. Add the chicken pieces, ensuring they are well coated. Cover and marinate for at least 30 minutes (or overnight in the fridge for better flavor).

In a large skillet, heat the vegetable oil and butter over medium heat. Add the finely chopped onion and sauté until soft and caramelized, about 8–10 minutes. Stir in garlic and ginger; cook for another minute until fragrant.

Sprinkle in cumin, coriander, smoked paprika, and garam masala. Stir well to toast these spices for about 2 minutes. This process magnifies their flavors!

Pour in the tomato sauce and bring it to a gentle simmer. Add the brown sugar, stirring until dissolved. Pour in the heavy cream, mixing until everything is fully incorporated. Allow the sauce to simmer and thicken for about 10 minutes.

While the sauce simmers, in a separate pan, sear the marinated chicken over medium heat until cooked through, about 5–7 minutes. Then, stir the chicken into the sauce, allowing it to simmer for another 5 minutes.

Taste the sauce and adjust seasoning if necessary before serving. Garnish with fresh cilantro and a sprinkle of lemon zest if desired. Serve this delightful dish with warm naan and rice.