Note : Don't use the coriander powder if you're using Rasam powder.
Blanch the tomatoes in 1 cup of boiling water for about 2 to 3 minutes. Donu2019t throw away this water but use it to soak the tamarind. Remove the tomatoes from the water and peel off the skin.
Cut the tomatoes into quarters, saving the pulp but throwing out the seeds. If all this seems like too much work, you can just cut the raw tomatoes into quarters and proceed from here onwards, but longer way makes for a tastier Rasam.
Pour the tamarind extract into a pan/ vessel and place on the stove. Add the tomatoes, curry leaves, turmeric powder and the salt and allow the tamarind and tomatoes to come to boil. Simmer for a few minutes till the tomatoes are cooked.
Add about 3/4 a cup of water to the dal and mix it so it that it becomes a watery dal-water mixture. Add this and the powdered jaggery to the above tamarind-tomato mixture. Once it boils, let it simmer for about 5 minutes. If the Rasam seems too thick in consistency add a little water to adjust to desired thickness. Rasam should have the consistency of a clear soup.
Now add the sambhar powder and coriander powder, after dissolving it about 2 tbsps of water. This will ensure that the powders mix well in the rasam. Just let it simmer for a minute. Do not allow the Rasam to boil too long after this point or the flavours of the spices will not come through. Take off the heat and add the coriander leaves.
Just before serving, heat the ghee or oil and add the mustard seeds. When they splutter, add the asafetida, take off the heat and pour this into the Rasam. Serve the Rasam hot, with rice, a tsp of ghee, pappad/ appalam (sun and a dried and deep fried crisps) dry vegetable preparation on the side.
To make the Rasam Powder, dry roast the above spices individually, till they give off an aroma. Take off the heat immediately, allow to cool a bit and grind into a powder.