Place chicken in a large bowl. Add ground turmeric, garam masala, black pepper powder, red chili powder, lemon juice and curry leaves. Season with salt. Using your hands, rub the marinade onto the chicken pieces. Chicken ver, and marinate in the refrigerator for at least an hour or overnight if possible.

Heat oil (for frying chicken) in a large frying pan over medium-high heat. Add chicken, and fry until golden and cooked through. Fry chicken in batches if needed. Drain onto an absorbent towel. Set aside.

Meanwhile, add onions to the same oil. Sauté for 2-3 minutes or until lightly browned. Add garlic, ginger and green chilies. Sauté for 2 minutes or until aromatic. Add ground turmeric, ground coriander, garam masala, and red chili powder. Sauté for 1 minute.

Stir in tomatoes (or canned tomatoes). Sauté for 2-3 minutes or until tomatoes turn mushy. Return fried chicken pieces to the pan. Stir. Cover and simmer for 3 minutes. Sprinkle over sugar. Stir and heat through. Garnish with more curry leaves.