1. Preheat oven to 375 F. Spray a large baking sheet with cooking oil spray.
2. Place the butter in a small microwave-safe dish, cover it with a paper towel, and microwave on high power until melted, about 15 seconds. Set aside.
3. Place 1 tortilla on the prepared baking sheet. Spoon the apple pie filling onto the tortilla and spread it out almost to the edge. Sprinkle cheese evenly over the filling. Place the second tortilla ove the apple mixture, forming a top crust.
4. Drizzle the melted butter evenly over the top crust of the quesadilla. Mix the sugar and cinnamon together in a small dish and sprinkle it evenly over the melted butter.
5. Bake until the quesadilla is crisp and the edges are just beginning to brown, 8 to 10 minutes. Remove it from the oven and, using a pizza cutter or a sharp knife, cut the quesadilla into 4 wedges, then serve.
Serves 4.