Nadan variety kadala is best suited for this.
Small brown kadala - 1 cup (soak in plenty of water with a pinch of soda overnight)
To grind:
Onions - 3 big, chopped
Soaked dhaniya - 2 tbsp
Red chillies - 5,6 (or to taste)
Tamarind - marble size
Grated coconut - 2 tbsp
Wash & pressurise the kadala directly in a pressure pan for 4-5 whistles till soft.
Cool & remove.
In the same pan, heat 1 tbsp coconut oil & fry the ground paste till the raw smell goes.
Add the cooked kadala, salt & correct amount of water to get the desired consistency.
Cook for one whistle.
Cool, open & add chopped coriander leaves.
It is optional to add 2 tbsp cooked kadala with the other grinding ingredients to get a thick gravy.