You can use 1 tablespoon of readymade tamarind paste and skip tamarind juice extraction.
Or, soak 1 tablespoon (big gooseberry size) of tamarind in ½ cup hot water for 10 to 15 mins.
Mash well with hands and strain the tamarind juice with hands. Add ½ more cup of water to the tamarind again, and extract the juice completely from the tamarind. Discard the fiber.
In a mortar pestle or mixie, place 1 tablespoon of coriander seeds, ¾ tablespoon of black pepper, 1 teaspoon of cumin seeds and 7 green chillies. Crush coarsely.
Top it with 7 garlic flakes. Crush roughly.
Add this crushed rasam powder to tamarind extract. Top it with 2 more cups of water.
Add enough salt, ¼ teaspoon of sugar, ⅛ teaspoon of asafoetida powder and turmeric.
Start heating over stove top. It will start to boil and become frothy.
Do not let it boil, just switch off the flame. Temper with 2 teaspoon ghee, ½ teaspoon mustard, 1 teaspoon cumin seeds and few torn curry leaves.
Mix to rasam. Garnish with a generous amount of coriander leaves and few torn curry leaves. Instant rasam without dal ready under 10 mins!