Preheat the oven to 350°F. Coat a mini muffin pan with non-stick cooking spray and set it aside.

Unroll the refrigerated pie crust onto a lightly floured surface. Cut out as many 2-inch circles as you can with a round cookie cutter. Gather the scraps, reroll them, and continue cutting until you've used all the dough.

Press each dough circle into the cups of the prepared mini muffin pan, gently shaping them to fit the bottom and sides.

Prick the bottom of each crust with a fork to help keep the shells from bubbling while baking.

Spray the inside of each crust with another coat of non-stick cooking spray.

Stir together the sugar and cinnamon in a small bowl, then evenly sprinkle the mixture over each pie crust shell.

Bake for 8 to 10 minutes, or until the edges are lightly golden. Remove the pan from the oven and let the tartlet shells cool for a few minutes before carefully lifting them out of the pan.

While the shells cool, prepare the filling. Add the diced apples, lemon juice, and butter to a small saucepan.

Cook over medium heat for 5 to 10 minutes, stirring occasionally, until the apples are tender but still hold their shape.

Stir in the sugar, caramel sauce, flour, cinnamon, and salt. Continue cooking for 3 to 5 minutes, stirring frequently, until the sugar dissolves and the filling thickens into a rich caramel coating.

Remove the saucepan from the heat and let the filling cool slightly so it's easier to spoon into the tartlets.

Fill each cooled pie crust shell with a generous spoonful of the warm caramel apple mixture.

Serve warm, or let the tartlets cool to room temperature before enjoying.