Wash dal thoroughly. Drain and rinse.
In a large soup pot, combine dal, turmeric, asafetida, and salt with 4 cups of water. Bring to a boil. Stir and cover pot with lid slightly ajar. Reduce heat to medium. Cook until softened, about 15 to 20 minutes. Set aside.
While dal is cooking, heat oil in a skillet over medium heat. Add cumin seeds. Heat until seeds are fragrant, turn brown, and start crackling, watching carefully. This will only take a minute.
Add red chilies and onions. Cook until lightly browned, stirring frequently.
Mix in ginger and garlic paste. Cook until mixture turns light brown, stirring occasionally to prevent onions from burning or sticking to the pan.
Add coriander powder and tomato purée. Cook another 3-4 minutes, stirring frequently.
Remove from heat and add onion and spice mixture to soup pot with cooked dal and stir to incorporate.
Place pot over medium heat, cook 3 to 5 minutes without the lid, stirring occasionally.
Garnish with chopped cilantro. Serve hot with rice or naan (Indian bread).
Moong beans are easy to cook, need little soaking, and are easy to digest.
This is not a yellow spilt pea. It is a lentil found in Asian or specialty grocery stores or online.