Marinate the chicken: In a bowl, mix yogurt, lemon juice, 1 tbsp ginger-garlic paste, garam masala, turmeric, cumin, and chili powder. Add chicken pieces and coat well. Cover and refrigerate for at least 2 hours, preferably overnight.

Cook the chicken: Thread marinated chicken onto skewers. Grill or broil for 10-12 minutes, turning occasionally, until slightly charred and cooked through. Set aside.

Prepare the sauce: Heat oil in a large pan over medium heat. Add onions and sauté until golden brown. Add remaining ginger-garlic paste and cook for 1 minute until fragrant.

Add tomato puree, sugar, and salt. Cook for 10-15 minutes until the sauce thickens and the oil separates from the mixture.

Finish the curry: Reduce heat to low. Stir in heavy cream and add the grilled chicken pieces. Simmer for 5-10 minutes until the chicken is heated through and the sauce is creamy.

Garnish with fresh cilantro and serve hot with naan or steamed rice.