First add oil in a kadai when it heats up add urad dhal kadalaparuppu and when it is brown add onion,chillies and ginger.
Add tamarind piece and salt and saute well,then add radish and mix.
Mix nicely for some time then sprinkle some water(1 tbsp approx) close the lid and cook.
When it become dry check for the veggie whether cooked.
Switch off and when cool add to mixer and grind with coconut scrapping(add needed water when grinding).
Do tadka and serve with idli and dosa.
Notes
We can make this chutney even without coconut.
Adding ginger to it masks the distinctive smell from radish.
You can increase spiciness according to your spice level.
Use tender radish so that it cooks quickly and we get tasty chutney.