In a large mixing bowl, combine the all-purpose flour, 1/3 cup sugar, baking powder, and salt. Use a whisk to ensure everything is evenly distributed and the flour is aerated, which helps with the fluffiness.
Add the cubed, cold butter to the flour mixture. Use a pastry cutter or two forks to work the butter into the flour until the mixture resembles coarse crumbs with some pea-sized pieces of butter remaining. These little bits of butter create steam pockets as they cook, making the scones flaky.
In a separate small bowl, whisk together the heavy cream, egg, and vanilla extract. Pour the wet mixture into the dry ingredients. Use a spatula to gently fold the dough until just combined. Do not overmix, as this will lead to tough scones.
Turn the dough out onto a lightly floured surface. Gently pat it into a circle about 1 inch thick. Use a sharp knife or a bench scraper to cut the circle into 8 even wedges.
Preheat your air fryer to 350°F (175°C). Place the scone wedges in the air fryer basket, leaving about an inch of space between them. You may need to work in batches. Cook for 8 to 10 minutes, or until the tops are golden brown and a toothpick comes out clean.
While the scones are cooking, mix the coating sugar and cinnamon in a small bowl. Once the scones are finished, remove them from the air fryer. While they are still warm, brush each scone generously with melted butter and then roll it in the cinnamon-sugar mixture until fully coated.