Pressure cook toor dal with turmeric and water until soft.

Whisk the cooked dal until smooth and set aside.

In a pressure cooker, combine chopped tomatoes, slit green chilli, ginger, coriander powder, cumin powder, turmeric powder, black pepper powder, salt, and water.

Pressure cook for one whistle, then release pressure naturally.

Add the cooked dal to the cooked tomato mixture.

Squeeze in lemon juice and stir in coriander leaves.

Adjust salt and spices to taste.

Heat ghee (or sesame oil) in a small pan.

Add mustard seeds and cumin seeds and let them crackle.

Add asafoetida powder and curry leaves, stir and turn off the heat.

Pour the tempering over the rasam.

Bring the rasam to a brisk boil for 2-3 minutes until frothy.

Adjust consistency with water if needed.

Check seasoning and lemon taste, adjust accordingly.

Serve hot with rice and a vegetable side dish.