Discard ½-inch pieces from the top and bottom and cut the onions into thin rings.
Soak the onion rings in ice-cold water for 2-3 minutes.
Drain the water completely.
Add Kashmiri red chili powder, chaat masala, salt, green chilies, cilantro, and lime juice to the bowl and mix well using your palms until the rings are separated and coated with the spices.