blanch the tomatoes into boiling water till tomato gets crack on its surface. Take it out from the hot water and keep it in another bowl. Let it cool down.
Grind the tomatoes along with beetroot to make a puree.
In a big pot, add tomato & beetroot puree, homemade rasam powder, onion, chopped coriander stems, fine chopped garlic, some curry leaves, tamarind paste, salt, turmeric powder, jaggery and 4 cups of water. Adjust the amount of water to your taste.
Cook all ingredients at medium heat for 10-15 minutes with lid on. Once it’s done, turn off the heat and leave it covered.
For tempering, heat oil in pan, when hot, add mustard seeds. It would start crackling, add curry leaves and hing. If you want more spicy, add red chili. Wait till it gets brown color.
Pour the tempering into cooked rasam and stir. Let it be covered for a minute.