Take whole spices and condiments (sabut), dry them as in step 2 below and then follow the process.
The recipe does not call for oil, to maintain authentic taste.
If you have a sunny balcony or terrace, spread the ingredients separately on clean sheets of plastic or newspaper, for at least one day, letting them soak in the sun. Remove before the sun goes down and the air becomes chill.
Check the ingredients for small stones, sticks etc. Remove the stalks from the red chilies.
Heat a suitable pan, and dry roast each type of ingredients separately for a few minutes on low to medium flame, taking each one to separate dry dish after roasting.
Roast the Coriander seeds for about 3 minutes, stirring frequently.
The Dals (lentils) should be sautéd together on a low flame till they darken slightly. Watch out while doing this as they can quickly burn and char to black.
The Cumin seeds should be roasted for only about 30 seconds and removed before they begin to blacken. The turmeric powder is to be sautéed dry for a few seconds, and I do this last, after all the other items have been roasted.
The dry red chillies will give a pungent smell so don't breathe in deeply when you are roasting them!
Once the roasted ingredients have cooled, you need to grind them. Coarse grinding is sufficient, except for the chilies.
Grind the coriander seeds first
Add the dals/ lentils and grind.
Add all the other ingredients except for the red chilies, and grind to a coarse powder.
Remove from the mixer/ processor and keep aside.
Grind the red chillies as fine as you can get them. Remove from processor.
Mix equal quantities of the red chilli powder and the coriander-spices mixed powder.
Mix well so that all the spices blend together completely.
Use in Rasam powder as per my recipe for Spicy Tomato Rasam https://www.pepperonpizza.com/spicy-tomato-rasam-recipe