Preparation: Preheat your oven to 400°F (205°C).
In a mixing bowl, combine your diced apples, sugar, ground cinnamon, and lemon juice. Mix until apples are well-coated.
Roll out the puff pastry on a floured surface to prevent sticking.
Cut the pastry into 4 squares.
Place a generous amount of apple filling (about 1/2 cup) in the center of each square.
Fold each pastry square over the apple filling, forming a triangle. Press the edges with a fork to seal them.
In a small bowl, beat the egg with water to make an egg wash.
Brush the top of each Apple Turnover with the egg wash. This will give it a golden-brown finish.
Place the turnovers on a baking sheet lined with parchment paper.
Bake in the preheated oven for about 25 minutes or until they're golden brown.