Start by coring the apple and then cutting it in half. Place the flat side of each half down on your cutting board. Carefully slice the apple into very thin half-circle or dome-shaped slices.
Place the apple slices into a bowl with water and microwave them for 45-60 seconds, until they are soft and easily bendable.
In a small bowl, mix together your desired amount of sugar and cinnamon to create a cinnamon sugar blend. Set aside.
Take your thawed puff pastry and roll it out on a lightly floured surface until it is thin. Cut the pastry into long strips, each about 2 inches wide and 9 inches long.
Brush a thin layer of melted butter onto each strip of puff pastry and sprinkle the cinnamon sugar evenly over the buttered pastry.
Lay the apple slices along the long side of the dough strip, overlapping them slightly and allowing about 1/2 inch of the apple slices to extend beyond the edge of the pastry.
Fold the bottom of the puff pastry strip up over the bottom of the apple slices, so the apples are tucked into the dough but still peeking out from the top.
Prepare an egg wash by whisking together one egg with 2 tablespoons of water. Brush the egg wash over the folded edge of the puff pastry.
Sprinkle a bit more cinnamon sugar over the egg-washed pastry.
Starting from one end, carefully roll the puff pastry strip tightly to create a rose shape.
Lightly butter or oil your cupcake or muffin tin. Place each apple rose into a prepared cup.
Preheat your oven to 375°F (190°C). Once preheated, bake the apple roses for 35-45 minutes. The baking time will vary depending on how thin and long you rolled the puff pastry. The pastry should be golden brown, and the apples should be tender.
Once baked, let the apple roses cool slightly. Sprinkle them with powdered sugar for a final touch, and enjoy!