To prepare tamarind semia, in a pan, bring 1 and 3/4 cups water to a boil with salt, tamarind paste, turmeric. (in case you are using tamarind water/extract, then reduce the water content accordingly)
When the water comes to a boil, add the roasted semia (vermicelli) and allow to cook on medium flame. Once the vermicelli is cooked and the water is absorbed, remove this in a plate and allow to cool. Do not overcook the semia.
Meanwhile, prepare the tempering for the Tamarind Semia. In a heavy bottomed kadai, heat the gingelly oil.
Add the mustard seeds. Once the seeds splutter, add udad dal, chana dal and peanuts. Stir on high flame until the dals turn golden brown and peanuts turn a shade darker and crisp up.
Add the curry leaves, red chillies, asafoetida - stir for few seconds. Then add the cooked semia, a little extra salt (1/4 tsp or as per taste), sugar and toss to combine well.
Remove this into a serving bowl and garnish with fresh coconut or finely chopped coriander leaves.