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

Cover and refrigerate for 30 minutes to an hour.

Preheat 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. Cook in batches if needed.

Spray the tops with cooking oil spray.

Air fry for 4 minutes.

Flip rings, spray again if needed, and cook for an additional 3 to 4 minutes until golden and crispy.

Serve immediately with lemon wedges and marinara sauce for dipping.