Combine dal, tomatoes, green chilies and 1½ cups of water in an Instant pot or pressure cooker. Cook on Manual under high pressure for 6 minutes or for 3~4 whistles.
Let the pressure release naturally.
If cooking in a saucepan, combine dal, tomatoes and green chilies in a heavy bottomed saucepan. Add 2¼cups of water, bring the mixture to a boil. Lower the heat, cover and cook till the lentils are soft, about 25~30 minutes.
Heat oil in a small sauce pan, add mustard and cumin seeds. After the seeds splutter, add red chilies and hing.
Add the seasoning, red chili powder, turmeric and salt to the cooked dal. If dal looks too thick, then add about ½~1 cup of water (depending on the desired consistency) to the dal and cook for about 5 minutes on saute mode in IP and on medium flame on the stove.
Add lemon juice and chopped coriander after removing from the flame and mix well.