Preheat a waffle iron according to manufacturer’s instructions. Spray inside of waffle iron with cooking spray.
Process garbanzo beans in a food processor until coarsely chopped. Add onion, egg whites, cilantro, parsley, garlic, flour, cumin, salt, coriander, black pepper, cayenne pepper, and cardamom to garbanzo beans. Pulse, scraping down the sides of the bowl occasionally, until falafel batter resembles a coarse meal. Pour batter into a bowl and stir with a fork.
Spoon about 1/4 cup falafel batter onto each section of the preheated waffle iron. Cook until evenly browned, about 5 minutes. Repeat with remaining batter.