Preheat your air fryer to 350°F (175°C).
In a large mixing bowl, whisk together the flour, baking powder, salt, granulated sugar, and cinnamon (if using).
In another bowl, combine the buttermilk, melted butter, egg, and vanilla extract. Mix well.
Gradually pour the wet ingredients into the dry ingredients, stirring until just combined. Do not overmix.
Lightly flour a clean surface and turn out the dough. Roll it out to about ½ inch thick.
Use a cookie cutter or donut cutter to cut out biscuit shapes and place them on a lightly floured surface.
Spray the air fryer basket with cooking spray, and arrange the biscuit shapes in a single layer. Depending on the size of your air fryer, you may need to cook in batches.
Air fry the biscuits at 350°F (175°C) for 5-6 minutes or until they are golden brown.
While the biscuits are cooking, prepare the glaze by whisking together the powdered sugar, milk, and vanilla extract in a small bowl until smooth.
Once the biscuits are cooked, transfer them to a cooling rack for about 2-3 minutes, then dip the tops in the glaze or drizzle it over the biscuits.