1.Boil some water. add salt and immerse citron. leave it for 5 minuties.
2.Remove and wipe well. cut into 1cm. pices. 3. Heat oil. add mustard seeds.
4. as seeds crackle, add chopped onion, green chillies and ginger. saute.
5. add red chilli powder. fry for 2 minuties longer.
6. add citron pieces. add salt and vinegar. bring to boil.
7. cook for a further 10 minuties and remove.