Preheat air fryer to 370 degrees F. Spray a silicone egg-bite mold with nonstick cooking spray.
Mix flour, sugar, water, egg yolk, butter, baking powder, vanilla extract, and salt together in a large bowl. Stir to combine.
Beat egg white in a small bowl using an electric hand mixer on medium speed until soft peaks form. Fold into batter. Add batter to the prepared mold using a small hinged ice cream scoop.
Place filled silicone mold into the basket of the air fryer.
Fry in the preheated air fryer for 7 minutes. Remove mold from the basket carefully;pop beignets out and flip over onto a parchment paper round.
Place parchment round with beignets back in the air fryer basket. Cook for an additional 2-3 minutes. Remove beignets from the air fryer basket and dust with confectioners' sugar.