Preheat and Prepare the Pastry
Preheat oven to 200°C (390°F).
Roll out the puff pastry on a lightly floured surface.
Prepare the Apples
In a bowl, mix the apple slices with sugar and cinnamon.
Assemble the Dessert
Arrange the apple slices over the pastry, leaving a small border.
Brush the apples with melted butter.
Fold the edges slightly over the apples for a rustic tart look.
Egg Wash and Bake
Brush the edges with beaten egg.
Transfer to a lined baking sheet and bake for 20-25 minutes, until golden brown.
Serve and Enjoy
Let cool slightly and dust with powdered sugar if desired.
Serve warm as is or with a scoop of vanilla ice cream.