In a vessel, take 1 cup of toor dal and add 3 cups water and a pinch of turmeric powder. Place this vessel inside a pressure cooker with little water under the vessel and cover it with a lid. Cover the cooker and allow for 3 whistles. If pressure cooker is not available, you may just boil in a vessel for a long time until the dal becomes soft like a paste. This is used for the preparation of sambar, rasam etc.
To this you may add 1/2 tsp salt. Splatter mustard seeds in ghee and add to the dal. Serve with rice. This is used for various festivals.