Place calamari rings in a large bowl and add the buttermilk; stir around to coat all the rings.

Cover and refrigerate for 30 minutes to an hour.

Preheat the air fryer to 400°F.

In a large shallow bowl, whisk together the coconut flour, cornstarch, oregano, salt, pepper, paprika, and cayenne.

Remove calamari rings from buttermilk and shake off excess.

Dredge the rings in the flour mixture.

Place rings in the basket of the air fryer in a single layer. You may need to cook in batches.

Spray the tops with cooking oil spray.

Air fry for 7 minutes.

Flip them over; spray with cooking spray and continue to cook for about 7 more minutes, or until browned and crispy.

Serve immediately with lemon wedges and marinara sauce for dipping.