Pressure cooker: Add dal to a bowl and rinse it well at least thrice. Drain the water and pour 1½ cups water. Place it in the cooker and pressure cook for 3 to 4 whistles on a medium flame. When the pressure releases remove the dal and mash it well to smooth.
Pot: To cook in a sauce pot without a pressure cooker, simply cook on a medium heat until tender and soft, skim off any foam that comes on the surface. You may require more water, if so pour more boiling water and cook.
To cook in Instant Pot, place the bowl in the IP, over a steam rack and pressure cook for 10 mins. Let the pressure drop naturally.
Dal must be soft cooked and mushy. Mash it well with the back of a ladle to smooth texture.
How to Make Lemon Rasam
While the dal cooks, pour 4 cups water to a pot. Add tomatoes, turmeric, rasam powder, green chilli (optional) and crushed ginger. Cook until the tomatoes are soft cooked and mushy.
Add the mashed dal and salt. Bring it to a boil & add chopped coriander leaves.
Heat a small tadka pan and add oil or ghee. When it is hot, add mustard seeds, cumin seeds, methi seeds and dried red chilies.
When the seeds begin to crackle, add curry leaves and hing. Pour it to the lemon rasam. Simmer the rasam for 2 mins on a very low flame.
Allow the lemon rasam to cool down a bit then squeeze off lemon as needed. Adjust salt as well.
Serve lemon rasam with soft cooked rice or enjoy as a soup.