Preheat oven to 160°C.
1 Wash chicken thoroughly and dry with paper towels. Sprinkle with salt and pepper, add masala and rub all over the chicken. Set aside.
2 Braise the onion in oil in a small pot until soft. Add mustard seeds, chilli powder, curry leaves, ginger and garlic. After 3 minutes add tomatoes and water and simmer for 20 minutes until tomatoes have softened into a thick sauce. Add salt to taste. Set aside.