In a kadai heat gingelly oil. Add mustard seeds and cumin seeds. Let them splutter.
Add fenugreek/methi seeds and fry to golden brown state. For any tamarind based gravy, adding methi seeds is an important step. Fenugreek has the property of balancing the acidity created by tamarind.
Add chopped onions and garlic. Fry onions until transparent color achieved.
Add turmeric powder.
Add chopped tomato. This is optional. As this karuvepilai kulambu is tamarind based gravy, this step can be skipped. I added tomato for some extra taste.
Once tomatoes turn mushy add karuvepilai paste and saute nicely. The raw flavor of curry leaves/karuvepilai should not be there.
Add sambhar powder. If sambhar powder is not available, ¾ tsp of red chilli powder can be added.
Add tamarind juice extract to the gravy. Filter out and discard the waste. Close the lid and let the kulambu boil for ten minutes until raw tamarind flavor goes off.
Add required stone salt. Adjust the consistency of the kulambu by adding some water. You can see the oil floating on top of gravy.
Add small jaggery piece and mix (I forgot to take picture). Switch off the stove at this stage.
Serve with hot steamed rice and potato fry or simple papad.