01 - Combine chicken with yogurt, lemon juice, turmeric, cumin, garam masala, chili powder, and salt in a large bowl. Mix thoroughly to coat, cover, and marinate for 10 minutes up to 1 hour.
02 - Heat 1 tbsp butter and vegetable oil in a large skillet over medium-high heat. Add marinated chicken and cook for 5-6 minutes, turning occasionally, until lightly browned but not fully cooked through. Remove chicken and set aside.
03 - Add remaining 1 tbsp butter to the same skillet. Sauté onions for 3-4 minutes until soft and golden. Add minced garlic and grated ginger; cook for 1 minute until fragrant.
04 - Stir in coriander, paprika, and cayenne pepper. Cook for 30 seconds to bloom spices. Add crushed tomatoes and sugar; simmer for 5 minutes, stirring occasionally.
05 - Return chicken and accumulated juices to the skillet. Simmer for 8-10 minutes until chicken is cooked through and sauce has thickened slightly.
06 - Reduce heat to low. Stir in heavy cream and simmer for 2 minutes. Adjust seasoning with salt to taste.
07 - Serve hot over steamed basmati rice or with warm naan bread. Garnish generously with chopped fresh cilantro.