Wash the tomatoes very well .In a kadai add in Water and bring it boil and add the tomatoes in it and allow it to cook till the skin of the tomatoes start peeling as shown in the image .switch off the flame and allow it to cool down.
Once the cooked tomatoes cool down with the help of the hands. Mash it well. Remove off the outer skin and retain the juicy tomato pulp along with the water.
Now in a Mortar and Pestle add in the Garlic pods, Cumin Seeds, and Pepper corns and crush it nicely.
In a Kadai add oil, once it heats up add in Mustard Seeds, Curry leaves and then add the crushed Garlic, Cumin, and Peppercorn fry for a min.
Add the tomato water, along with this add the tamarind water as well. Next add in Rasam Powder, Turmeric powder and Salt.
Mix it well and allow it to cook till it comes to a boil add in coriander leaves and switch off the flame.
Notes
Tastes good when served with Steamed rice and Potato Fry.
It is a good medicine during cold and cough. It soothes the throat.