I have been making this Rasam powder for a long time now. It is easy to prepare, lasts long and the Rasam comes out very tasty too. I learnt it from my mother. All the ingredients are raw (not roasted or fried). You can vary the proportions slightly, depending on the availability at home and the taste does not alter too much. Dry ginger is optional.
Dhania (Coriander seeds) – 2 tbsp.
Jeera (cumin seeds) – 1.5 tbsp.
Black peppers – 1 tsp.
Toor dal (Pigeon Pea) – 3 tbsp.
Dry ginger – 1 cm. piece
Dry grind all the ingredients to a coarse powder in the mixie. Store in a glass bottle.