Start by lightly flouring your work surface. Unroll the thawed puff pastry sheet and cut it into squares (4 or 6 squares, depending on the desired size of your turnovers).
Preheat your air fryer to 350°F (175°C). This ensures that the turnovers will start cooking immediately and get a nice, even browning.
Spoon about 2 tablespoons of cherry pie filling onto one half of each puff pastry square. Be careful not to overfill, as the filling could spill out during cooking.
In a small bowl, beat the egg and brush the edges of the pastry squares with the egg wash. This helps to seal the turnovers.
Fold each square in half diagonally to form a triangle. Press the edges together to seal, and use a fork to crimp the edges, ensuring they are well sealed.
Brush the top of each turnover with more egg wash for a golden finish. Sprinkle with a mixture of brown sugar and either ground cinnamon or turbinado sugar for added sweetness and texture.
Place the turnovers in the air fryer basket, leaving space between each one for the air to circulate (cook in batches if necessary).
Air fry for about 15-18 minutes, or until they are golden brown and puffed up. The exact time might vary depending on your air fryer model.
Let the turnovers cool for a few minutes after cooking, as the filling will be very hot.
Serve warm and enjoy!