Dice the tomatoes, roughly chop the cilantro.
Heat oil in a pan and add cumin seeds.coriander seeds, green chillies, red chillies, chopped ginger one by one and saute till the coriander seeds turn light brown. Add coconut and saute again for few seconds. Keep it aside and allow it to cool. Grind to a smooth paste by adding little water.
Heat one cup of water in another deep vessel and add diced tomatoes, salt and jaggery. Cook till the tomatoes are soft.
Add the ground masala along with chopped cilantro, and tamarind paste. Add enough water to make it medium thick and bring it to a boil.
Lower the heat and cook for about 5 minutes.
Now heat oil in a pan and add mustard seeds. When they splutter, add curry leaves and asafoetida. Saute for about 5 seconds. Pour it over the tomato mixture and cover the pan immediately. Serve hot with steamed white rice.