Roast all the ingredients separately until they turn golden brown and start releasing their aroma. Roasting separately prevents from getting them burnt.
Once they cool down, grind it in a spice grinder / mixer into a smooth powder.
Shelf life for Rasam powder: Store them in an air tight container. They stay good for months.
Rasam Powder | Rasam Podi https://www.themagicsaucepan.com/sides/spice-mix/rasam-powder-rasam-podi