Preheat the oven to 375°F / 176°C.
Cut the apples into two portions and then halve again into quarters. Slice them into really thin pieces. Take a large microwaveable bowl and add the apple slices. Fill with water and squeeze over the lemon juice.
Now heat the apples in the microwave for at least 3 minutes until they are a little softer.
Take a small bowl and combine the sugar and cinnamon.
Strain the excess water from the apple slices and pat them dry. Add them to the cinnamon and sugar mixture and mix the everything together well. Be careful not to break the apple slices.
Now cut the puff pastry into long strips. Place at least 8 or 9 apple slices on the top half of the puff pastry strips skin-side up. The width of the strips should not be more than 2 inches.
Brush the puff pastry with egg yolk and then sprinkle a little of the ground almonds on the bottom half of the pastry.
Next, fold the bottom half of the puff pastry over the apple slices and then, starting from one end, tightly roll the puff pastry with the apples, and suddenly you will notice it's already looking like a pretty apple rose.
Now take a muffin pan and brush it with some melted butter, or you can also use regular oil spray, and then place those cute apple roses in each hole.
Place the muffin pan on the middle rack of the oven and let them bake for 35 minutes or until the pastry becomes crisp and golden brown and the apple slices are cooked through.
When the apple rose tarts are fully baked, remove them from the oven, transfer the pastries to a wire rack and let them cool for a few minutes. Lastly, sprinkle some powdered sugar on these pretty apple roses and garnish them with beautiful rose petals.