01 - Combine yogurt, lemon juice, cumin, coriander, garam masala, chili powder, and salt in a large bowl. Add chicken pieces and toss thoroughly to coat. Marinate for 15 minutes at room temperature or up to 2 hours refrigerated for deeper flavor penetration.
02 - Heat 1 tablespoon butter and neutral oil in a large skillet over medium-high heat until shimmering. Add marinated chicken pieces in a single layer and cook for 5 to 7 minutes, turning occasionally, until browned on all sides and nearly cooked through. Transfer chicken to a plate, reserving any juices.
03 - In the same skillet, add chopped onion and sauté for 3 to 4 minutes until softened and translucent. Add minced garlic and grated ginger, cooking for 1 minute until fragrant but not browned.
04 - Stir in crushed tomatoes, cumin, paprika, garam masala, chili powder, sugar, and salt. Reduce heat to medium and simmer for 10 minutes, stirring occasionally, until sauce thickens noticeably and deepens to a rich red color.
05 - Reduce heat to low. Pour in heavy cream and add 2 tablespoons butter, stirring constantly until butter melts completely and sauce becomes smooth and velvety. Avoid boiling at this stage to prevent separation.
06 - Return chicken and any accumulated juices to the pan. Simmer gently for 5 to 7 minutes over low heat until chicken is fully cooked through and flavors have melded. Sauce should coat the back of a spoon.
07 - Sprinkle generously with chopped fresh cilantro. Serve immediately while hot, accompanied by basmati rice or warm naan bread for soaking up the sauce.