Take water in a bowl and add corriander powder, turmeric powder and chilly powder or alternatively add only sambhar powder and mix well.
Add tamarind water with additional 1 cup of water and boil it. While boiling also add tomato, onion,salt and allow it to boil for 5 minutes till it forms into a semi liquid consistency. Add sugar to temper the tanginess of the tamarind water.
Heat the oil in a kadai. Add mustard, dry red chilly, methi seeds and when mustard splutters add curry leaves.
Pour this seasoning unto the curry.
Serve the curry with chapathis.