In a large bowl, combine yogurt, lemon juice, 2 teaspoons garam masala, 1 teaspoon cumin, coriander, 1 teaspoon chili powder, and salt. Add chicken pieces and toss to coat. Marinate for at least 15 minutes or overnight in the refrigerator.

Heat 1 tablespoon butter in a large skillet over medium-high heat. Add marinated chicken and cook for 6 to 7 minutes until browned on both sides but not fully cooked through. Remove to a plate.

Melt remaining 2 tablespoons butter in the same skillet over medium heat. Add chopped onion and saute for 5 to 6 minutes until golden brown and softened.

Add minced garlic and grated ginger. Cook for 1 minute, stirring constantly, until fragrant.

Stir in remaining garam masala, cumin, paprika, turmeric, and chili powder. Cook for 30 seconds, stirring constantly, to bloom the spices and release their essential oils.

Pour in tomato puree and stir to combine. Season with salt, pepper, and sugar if using. Simmer for 10 minutes, stirring occasionally, until sauce thickens slightly.

Reduce heat to low and stir in heavy cream until well combined. Cook for 2 minutes to warm through, being careful not to let it boil.

Return chicken and any accumulated juices to the skillet. Simmer gently for 10 to 12 minutes over low heat until chicken is fully cooked through and reaches 165°F internally.

Taste and adjust seasoning if needed. Garnish with fresh cilantro and serve hot with naan, basmati rice, or cauliflower rice.