Once the oil is hot, add hing, zeera, mustard seeds, kalonji, methi seeds and green chilli and let them crackle for a few seconds.
Add ginger, chopped tomato, salt and red chilli powder and cook for 10-12 minutes.
Add jaggery and cook for another 4-5 minutes until the chutney thickens and become dark in colour.
Store the chutney in refrigerator for upto a week.
To make Bengali Sweet and Sour tomato chutney, heat mustard oil in a pan. Add panch phoran and ginger and fry for a few seconds.Add chopped tomatoes. Cover and cook for 8-10 minutes. Add salt, sugar and water and cook for another 2-3 minutes.