Slice onion crosswise in ½" sections to make rings. Separate the nested rings of each slice. Spray a sheet pan with nonstick cooking spray. Spread onion rings onto the sheet pan.
Fill each onion ring with 2-3 tablespoons of guacamole. Spread the guacamole smooth under the top edge of each round.
Place the sheet pan with filled onion rings into the freezer and freeze for about 1 hour until the guacamole is solid.
Prepare a standard dredging station.
Combine the flour, pepper, chili powder, and salt in a shallow bowl.
Beat together the buttermilk and eggs in a second shallow bowl.
Place the panko breadcrumbs in a third shallow bowl.
Dip each frozen onion ring into the flour mixture, coat with the egg mixture, and cover with the panko.
Air Fryer Guacamole Stuffed Onion RingsSpray the bottom of the air fryer basket with nonstick cooking spray.
Place the coated onion rings in the air fryer's basket and spray liberally with nonstick cooking spray.
Cook at 360°F for 12-14 minutes, until the coating is golden brown and crispy. You can flip the onion rings halfway through cooking for a more evenly browned coating, but this can be a bit tedious as the guacamole heats and softens. The onion rings will cook through without flipping them.
Plate, serve, and enjoy!