Soak dal in 1 cup of hot water for 15 minutes
Cook dal with a pinch of turmeric powder (save some) in a pressure pan until soft. Mash well and put to one side
Add a cup of water, the rest of the turmeric powder, rasam powder, tomatoes, green chilli, ginger, salt, and curry leaves
Bring to boil then simmer for 15 minutes
Mix in the cooked dal with a cup of water
Simmer further until you see froth forming on the top then remove from heat
Stir in lemon juice
Add the ghee, mustard seeds, cumin seeds, and curry leaves
Serve and garnish with coriander leaves