Cook the tomatoes, spices, salt, water and curry leaves together on medium high heat till the tomato pieces are soft, about 6-8 minutes.
In the meantime, grind coconut, cumin seeds and mustard seeds together using just enough water to a smooth paste. Mix this ground paste with the curd and set aside.
Once the tomato pieces are cooked, add the ground paste to it and cook till it begins to steam and froth a bit on the sides. Do not let it boil. Take it off the heat.
In a small skillet, heat the oil and crackle the mustard seeds followed by the curry leaves and chilies. Pour over the pacchadi and serve hot with rice!
By Ria Samuel