Clean, wash and soak the toovar dal in enough water in a deep bowl for 2 hours and drain well.
Combine the toovar dal, salt, turmeric powder and 1 cup of water in a pressure cooker, mix well and pressure cook for 2 whistles.
Allow the steam to escape before opening the lid. Keep aside.
Combine the besan and curds in a small bowl, whisk well and keep aside.
Heat a deep non-stick pan on a medium flame and when hot, add the cumin seeds and dry roast for about 30 seconds.
Add the onions and dry roast for 1 to 2 minutes or till they turn light brown in colour. Sprinkle a little water if the mixture starts burning.
Add the cooked dal, chilli powder, coriander powder and cumin seeds powder, mix well and cook on a medium flame for 1 minute, while stirring occasionally.
Lower the flame, add the curds-besan mixture, ½ cup of water and little salt and mix well. Cook on a slow flame for another 1 to 2 minutes, while stirring occasionally.
Serve immediately garnished with coriander.