Gently toss the Hidden Rose Apples® (3), Granulated Sugar (1 tablespoon), Rose Water (1/2 teaspoon), and Ground Nutmeg (1/4 teaspoon) together in a large pot and heat over medium heat for about 7 minutes or until the apples are just flexible.
Remove from heat and cool to room temperature.
For the pastry, while the apples cool, preheat the oven to 375 degrees F (190 degrees C) and line two baking sheets with parchment paper.
Add the Pistachios (1/2 cup) to the bowl of a food processor. Process until finely ground.
Add the Granulated Sugar (1/4 cup), Rose Water (1/2 teaspoon), Ground Nutmeg (1/4 teaspoon), and Salt (1 pinch) to ground pistachios. Pulse for about 10 seconds to incorporate.
Flour your work surface. Gently roll one sheet of Puff Pastry (1 package) with a rolling pin until smooth and large enough to cut out 2 6-inch rounds.
Repeat with the second sheet of puff pastry and place puff pastry rounds onto the parchment lined baking sheets.
To ensure the tarts will have a puffy outside crust, lightly score a border around the entire edge (about 1/2-inch in width) with a paring knife and then prick everything inside this border with a fork.
Evenly divide the ground pistachio blend onto the four pastry rounds, spreading it evenly across the inner circle of your puff pastry rounds.
Arrange the cooled apple slices on top of the ground pistachio blend, starting on the outside of the circle, working your way into the center.
Sift each tart with Powdered Confectioners Sugar (1 tablespoon) and then bake the tarts on the centermost racks of the oven for 20 minutes, rotating the baking sheets 1/2 way through.
While the tarts bake, whip the Heavy Cream (1 cup) with the Granulated Sugar (1/4 cup) and Ground Cardamom (1/4 teaspoon) until they become soft peaks.
Once the tarts are done baking, let them cool at room temperature for about 10 minutes and then serve with generous scoops of the cardamom whipped cream on the side.