This is a recipe which my mom have given me and which she have been making for more than 35 years. The rasam that is made using this rasam powder have been a hit amongst our family and friends. I too follow the same recipe.

Coriander seeds (Dhaniya) - 3 cups

Thuvar Dal - 1 3/4 cups

Red Chillies - 1 1/2 cups

Black Pepper - 1 cup

Cumin Seeds (Jeeragam) - 1 cup

Asafodeita piece - 2 inches

Turmeric Powder - 1/4 cup

Note: If long thin red chillies are used, then 3 cups of chillies can be used.

Fry all the ingredients separately in a dry pan. Let it cool and grind it in flour mill (or to a fine powder in mixie). Let it cool and add the turmeric powder and mix thoroughly. Store it in air tight container.