In a shallow pan heat oil and fry the chicken pieces on high heat. Lower heat, add ginger / garlic paste, stir and cook. Add tomatoes and simmer for 5 - 6 minutes. Stir and add the chilli powder and salt, mix well. Cook till oil separates from spices. Onion mixture: In a saucepan heat oil and fry onions on medium heat until light brown. Add cumin seeds, green chillies and coriander powder, continue to cook on low heat for a few more minutes. Add the onion mixture to chicken gravy, stir to mix on medium heat, add a little hot water to the gravy. Cover the saucepan and simmer for 10 minutes on low heat. Sprinkle garam masala powder on chicken before serving.