Preheat the oven to 350ºF. Peel and chop the apple into ½-inch pieces.
Melt the butter in a small skillet over medium heat. Once melted, add the chopped apples, brown sugar, and cinnamon. Sauté the apples in the butter and brown sugar until they're softened and the brown sugar has reduced into a sticky caramel (about 10 minutes).
Score the top of the wheel of brie in a hatch pattern (you can also remove the top layer of rind, or leave it whole). Place the brie in a small baking dish, then pour the caramelized apples over top. Sprinkle the chopped pecans on top.
Bake the brie in the preheated oven for 15 minutes. Enjoy the brie hot with crackers, bread, or apple slices.