Marinate the Chicken:
In a large bowl, mix yogurt, lemon juice, and all the spices. Add the chicken pieces, coat well, and refrigerate for at least 30 minutes or overnight.
Prepare the Sauce Base:
Melt butter in a skillet over medium heat. Add onion and sauté until soft and golden. Stir in garlic and ginger and cook for 1 minute until fragrant. Transfer mixture to the crockpot.
Add Chicken and Tomatoes:
Place marinated chicken in the crockpot. Pour in tomato sauce and stir to combine evenly.
Slow Cook:
Cover and cook on LOW for 6–7 hours or HIGH for 3–4 hours, until chicken is tender and fully cooked.
Add Cream:
Stir in the heavy cream and sugar. Let cook uncovered for another 10–15 minutes on LOW until thickened slightly.
Serve:
Garnish with fresh cilantro. Serve hot with steamed rice, naan, or over quinoa for a light twist.