Soak green gram in 2 cups hot water for 1 hour. Then, drain away the water and pressure cook with 1.5 cups of fresh water upto 2 to 3 whistles.
Take a pan or kadai, heat it and add oil. Once oil is heated up, add mustard seeds. Let them splutter. Add cumin seeds and let them turn brown. Next add turmeric powder, asafoetida, green chillies and curry leaves. Saute for a few minutes.
Next, add the chopped onions and saute until they turn light brown. Now, add chopped tomatoes and saute until they turn soft but not mushy. You can add some salt at this point so as to speeden up the cooking process.
Once onions and tomatoes are cooked well, add red chilly powder and cooked green gram. Mix everything well. Add more salt if required. Leave it dry or add some water and simmer for about 5 minutes in low-medium heat. If you find it to be thick add some more water and simmer until desired consistency .
Finally, turn off the heat and add chopped coriander. Serve with chapati or jowar roti.