Sprinkle flour over the countertop for rolling out the puff pastry. Unfold and cut the pastry in half. Place the second half back in the refrigerator while you work with the first half. Roll out into a 12 x 15 rectangle. Cut out five 5-inch circles. Transfer them to a baking sheet lined with parchment paper, then slide it back into the refrigerator. Repeat this step with the other half. You'll have a total of 10 circles. (If you're using the puff pastry that comes in two pieces, there's no need to cut them in half, just roll out each piece into a 12 x 15 rectangle.)
Peel and core the apples, cut into 1/4-inch slices. Scoop into a bowl and toss with the cinnamon and sugar.
Working with one baking sheet at a time, arrange the apple slices in a spiral pattern on the pastry circles, leaving a generous 1/4-inch border all the way around. Fold the edges up over the apples toward the center, gently pleating the dough. Brush the edges with egg wash. then dot each tart with small pieces of butter. Return the tarts back to the refrigerator. (If at any point the pastry gets too soft to work with, just refrigerate until it firms back up.) You'll need to refrigerate the tarts for at least 30 minutes before baking.
Preheat the oven to 425 degrees. Place the tarts in the oven and bake for 20 to 25 minutes or until golden brown. Remove from the oven and carefully transfer the tarts to cooling racks. Drizzle on the warm cajeta and sprinkle the chopped pecans over the top. These tarts are delicious served warm or at room temperature.