Preheat the oven to 400 degrees F.
Add diced apple into a large mixing bowl.
Stir in orange juice and orange zest and toss to combine.
Add in brown sugar, all-purpose flour, cinnamon, nutmeg, and kosher salt.
Stir to combine.
Flour a board and lightly roll each sheet of puff pastry to a 12 by 12-inch square.
Cut each sheet into 4 smaller squares and keep chilled until ready to use.
In a small bowl whisk together a large egg and water.
Brush the edges of each square with the egg wash and neatly place about 1/3 cup of the apple mixture on half of the square.
Fold the pastry diagonally over the apple mixture and seal by pressing the edges with a fork.
Transfer to a sheet pan lined with parchment paper.
Brush the top with egg wash and sprinkle the tops with Turbinado sugar.
Make 2 small slits in the top of each turnover.
Bake for 20 minutes or until browned and puffed.
Serve warm or at room temperature.