Soak tamarind and salt and in water and squeeze out the juice completely by adding water little by little. The tamarind juice should be at least 2 cups.
In a kadai put the oil and when it is hot add mustard. When it pops up add Bengal gram dhal. When it turns light brown, add fenugreek and fry till it become light brown. Keep the flame to very low. (Otherwise fenugreek will become black and taste very bitter). Cut the onion into small pieces and add along with curry leaves. Fry till onion turn transparent. Now add tamarind juice along with sambar powder and turmeric powder. Stir well. Allow to boil on a medium flame till it thickens.
