Wash and soak the whole brown lentils for 2–3 hours. Drain.
Pressure cook the soaked lentils with 2 cups water for 2 whistles (or 8–10 minutes on high pressure in an Instant Pot with natural release). Let the pressure release fully.
Heat oil in a kadai or skillet. Add mustard seeds and let them sputter, then add cumin seeds.
Once the cumin crackles, add curry leaves, asafoetida, and the slit green chili. Stir.
Add chopped onion and sauté until pink and translucent.
Add chopped tomato and cook until soft and mushy.
Sprinkle in salt and mix, then add turmeric powder.
Add the cooked lentils and grated coconut, mixing well.
Simmer for 5 minutes on low heat. Taste and adjust salt.
Make sure you're using whole brown lentils (sabut masoor), not split masoor dal, for the right texture.
Keeps refrigerated for 3–4 days, making it a good meal-prep option.