Place a small nonstick sauté pan over medium heat. Add the coriander and dry-roast until lightly browned and fragrant. Tranfer to a bowl.
Add one spice at a time, dry-roast the cumin and ajwain, and add them to the coriander. Stir and set aside to cool completely.
Transfer to a spice grinder. Add the chiles, black salt, citric acid, amchur, table salt and pepper. Grind to a fine powder.
Store in an airtight container.