Recipe for this powder came from my friend's mom, as I mentioned in my previous post. I have found that it is incomparable to any of the store-bought ones.
Dry coriander seeds - 2 cups
Dry Red chillies - twice as much as you can grab with your palms, say 2-3 cups
Poppy seeds - 2 tight fistful [about 2 tbsp]
Dried curry leaves - 1 cup [packed lightly]
Methi seeds - 1 tbsp
Asafoetida - 1/2 tsp
Dry roast each of the above ingredients, slowly in a thick bottomed pan (preferably cast-iron) at very low heat. It is important to roast each of these separately and without using any oil. Allow them to come to room temperature. Add 1-2 tbsp Jeera (un-roasted) to these and 1/4 tsp salt. Grind coarsely in the mixie and store tight in the refrigerator and use within 1 and 1/2 months for best results.
Make Sambar according to these instructions.
ETA: To make the measurements more clear. When I make sambar powder again in a few more days/weeks, I'll measure and update the dry chillies measurements in cups too.