For making rasam powder:
1)Make sure the ingredients are dry.
Grind them into a smooth powder(except for turmeric powder).
Add turmeric powder and mix well.
:-Avoid moisture content and you can keep it for months.
For making rasam:
1)Cook the red gram in a pressure cooker and mash it well.
Take 11/2 cups of water in a vessel and add salt and rasam powder to it.
If tomatoes are being used, cut them into small pieces and cook for a few minutes in this water along with green chillies.
When it starts boiling, add tamarind paste and boil for 5 more minutes.
Add the cooked red gram and boil further for 5 minutes.
When the rasam starts emitting a very good aroma, switch off the flame.
Add curry leaves and coriander leaves.
Sprinkle asafoetida powder.
Finally, crackle mustard seeds in ghee and add to the rasam.