Place onion in a small bowl. In a small pot, bring vinegar, salt, and sugar to a boil over medium-high heat. Pour vinegar mixture over onion. Refrigerate for 2 hours and let cool completely until ready to use.
In a large bowl, combine pork belly, Cajun seasoning, and baking soda, stirring until well coated.
Preheat air fryer to 250°.
Arrange pork belly in an even layer in air fryer. Cook for 15 to 20 minutes. Turn pork belly chunks.
Increase temperature to 400°. Cook, shaking air fryer basket occasionally, until golden brown and crispy, 15 to 20 minutes. Serve hot with pickled red onion.
Notes
*We used Slap Ya Mama Cajun Seasoning.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/air-fried-cracklins/