Add the washed and soaked tur dal to a pressure cooker with enough water and turmeric powder. Cook for 3-4 whistles over high flame. Let the cooker depressurize naturally, then whisk the dal until smooth and watery.

In a stock pot, heat oil and add red chillies, mustard seeds, curry leaves, green chilli, and garlic. Stir well and cook briefly.

Add asafoetida, tomatoes, salt, and coriander stems. Cook until the tomatoes are mushy. Then add turmeric powder, tamarind pulp, and jaggery with hot water. Cook for 3-4 minutes.

Add the cooked tur dal and adjust the consistency with more hot water if needed. Let the rasam simmer for 7-8 minutes, adding more water if it thickens. Dissolve rasam powder in water, stir into the rasam, and cook for 2-3 minutes. Adjust salt, add black pepper and fresh coriander.

Soak urad dal for 3-4 hours. Drain excess water and grind the dal coarsely in a mixer grinder with minimal cold water. The batter should be slightly coarse.

Transfer the batter to a bowl and whisk for 3-4 minutes until light and fluffy. Test if the batter floats in water to ensure it's ready.

Add salt, ginger, green chilli, asafoetida, and curry leaves to the batter. Mix gently.

Heat oil in a kadhai to 170°C. Dip your hand in cold water, scoop a small portion of batter, and carefully drop it into the hot oil. Fry the vadas over medium flame, flipping regularly, until golden brown and crisp. Remove and drain on a sieve.

Add a few vadas to a bowl and pour hot rasam over them or add the vadas directly into the rasam after frying.