Peel the onion and chop finely.
Cut the tomatoes in medium sized or small pieces.
To cook the green moong dal, wash the green dal and transfer it to a pressure cooker.
Add salt and water, close the pressure cooker with lid( and safety valve) and cook for about 6 to 7 minutes or until 2 whistles have come.
After 7 minutes of cooking, switch off the stove and wait for the pressure cooker to cool down.
To prepare the seasoning, Meanwhile heat oil in a pan and add mustard seeds.
When the mustard seeds splutter, add the broken dry red chilies and curry leaves, fry for a few seconds.
To prepare the curry, Add the onion and salt and cook in medium heat for about 5 to 6 minutes or until the onions turn transparent or little browned for even better taste.
As the onions are transparent in color or lightly browned, add the green chili, garlic and chopped tomatoes and cook for another five minutes or until the tomatoes are cooked and soft. Switch off the stove and keep the pan away from heat.
If the pressure cooker is cooled enough, open the cooker and see if the green moong dal or cherupayar is cooked enough and soft. If there is any water left, you may not need to add more water for the gravy. If there is no water left after cooking the green moong dal or if you think there is less water to make the gravy, add more water to make the gravy as needed.
Now add the cooked onion tomato mixture to the green moong dal in the pressure cooker and mix everything well. As I already mentioned above, if there is no enough water to make the gravy, please add more water as you need for the curry gravy.
Add all the spices to the green moong dal in onion tomato mixture in the cooker, and mix everything well.
Turn on the stove and bring the mixture to a boil, then reduce the heat to low and cook for another 2 more minutes, stirring in between so as to avoid burning the curry at the bottom of the pan.
Green moong dal curry or cherupayar curry without coconut (made with onion tomato mixture) is ready to serve!