Slice off the onion stem and set the onion on the flat side. Cut an inch from the root down, into 12 to 16 sections, being careful not to cut all the way through. Flip over and gently pull out sections of onion to separate petals.
In a shallow bowl, whisk together eggs and 1 tablespoon of water. In another shallow bowl, whisk together breadcrumbs and spices. Dip onion into egg wash, then dredge in breadcrumb mixture, using a spoon to fully coat. Drizzle onion with oil.
Place in the basket of the air fryer and cook at 375° until the onion is tender all the way through, 20 to 25 minutes. Drizzle with more oil as desired.