In a large bowl, combine the chicken pieces with ginger-garlic paste, half the red chili powder, turmeric powder, and salt. Mix thoroughly and marinate for at least 30 minutes in the refrigerator.

Heat oil in a heavy-bottomed pan over medium heat. Add mustard seeds and cumin seeds, allowing them to crackle.

Add curry leaves and chopped onions. Sauté until onions turn golden brown, about 8-10 minutes.

Add remaining red chili powder and coriander powder. Stir for 30 seconds to toast the spices.

Pour in tomato puree and cook until oil separates from the masala, about 10-12 minutes, stirring frequently.

Add marinated chicken and increase heat to medium-high. Stir well to coat with masala.

Cook uncovered for 5-7 minutes, stirring occasionally, until chicken begins to brown.

Add tamarind paste and 1 cup water. Mix well, bring to boil, then reduce heat to low. Cover and simmer for 20-25 minutes.

Uncover and cook for 5 more minutes to thicken gravy. Sprinkle garam masala and stir.

Garnish with fresh coriander and serve hot with rice or naan.