Preheat Oven to 325 Degrees F.

Grease a muffin tin with nonstick spray or butter

In a heavy pot over medium heat, cook the sugar and water together. Stir every few minutes until caramel turns yellow or amber color (about 5 minutes)

Remove from heat and add the butter. Careful because caramel can splash. Mix with a spoon until combined

Pour caramel into each muffin tin. Let it cool for a few minutes

Arrange the apples on top of the caramel

Bake for 30 minutes

Meanwhile, using a cookie cutter or the rim of a glass, cut out puff pastry circles. Freeze the unused Puff Pastry

After 30 minutes have elapsed, open the oven door and carefully place the puff pastry circles on top of each tart

Bake for 20 minutes more

Remove from oven, let them cool for 2-3 minutes and unmold onto a plate

Enjoy!