Grind toor dal to fine powder. I grind dal to fine powder and add it to rasam instead of cooking the dal and then adding it to rasam. This saves some time and this is a tip I picked up from my mother-in-law.
Heat oil in a 2 quart/liter sauce pan and temper it with mustard seeds, cumin seeds and curry leaves.
Then add ginger garlic paste and sauté until raw smell of ginger is gone.
Add turmeric powder, toor dal powder and roast the powders for a minute or two until the toor dal is lightly roasted in the oil.
Add V8 juice, salt, pepper powder (can add pepper after tasting the rasam), rasam powder, tamarind paste and mix well. Add water, tomatoes, cover the pan and bring to a boil.
Once rasam comes to a boil, taste rasam and adjust salt, pepper and tamarind paste to taste.
Partly cover the pan and continue boiling for another 3-5 minutes until tomatoes are soft.
Add cilantro, turn of the heat and cover the pan completely. Let it sit for another 5-10 minutes and serve hot with rice.
This soup a little light and mild, and can be served as soup as well.