Take the Urad dal, red chillies and cumin seeds together and roast them
Wait till the urad turns light brown in colour
Take onions and chop them to small pieces
Roast these chopped onions in a separate bowl
Once onion is sufficiently roasted, put them along with the Urad dal in a mixer grinder
Pour little water into the mix so that it becomes a paste
Add some salt and mix it with tamarind puree
Grind the entire mix for some more time
You can also mix a tadka of mustard seeds, asafetida, curry leaves to this chutney and mix it well.
The chutney can be kept in the refrigerator to serve cold if required.