Heat oil in a pan or a kadai.
Add small onions, ginger and green chillies and fry, till the small onions turns pink.
Add tomato and continue stirring, till it becomes tender.
Add kudam puli and salt.
Pour just enough water to cover and cook the tomatoes.
When the tomatoes are cooked, remove from flame.
Allow it to cool.
Grind together coconut and cumin seeds.
Add the coconut paste to the curry and keep on low flame.
Simmer for 5 mins to make the coconut paste blend into the curry.
Heat oil in a small pan.
Splutter mustard seeds, dry red chillies and curry leaves.
Pour this over the curry.
:- Serve hot with rice.