1. Pressure cook dal. Mash cooked dal.
2. Add 1 or 2 cups water and boil onions, salt, turmeric and green chillies for 5 minutes. Then add mashed dal slowly, mix well and cook for few minutes and then add lemon juice cook for few seconds and then remove from heat.
3. Heat oil, add red chillies, cumin seeds, mustard seeds, when cumin starts to splatter add asafoetida, chilli powder , garlic pieces and curry leaves. Remove from heat and add seasoning to rasam.
Garnish with coriander leaves.

Serve with rice.