Preheat oven to 350°F. Pour apple cider into the bottom of a 9 x 13-inch baking pan, set aside.
Place butter in a microwavable bowl and microwave on HIGH 30 seconds or until butter is melted. Stir brown sugar, walnuts, raisins, cinnamon and vanilla with the melted butter; set aside.
Cut apples in half lengthwise and remove apple cores with a melon scooper. Remove stem using a pairing knife. Place the apple into the prepared baking pan. Divide the filling mixture evenly among the apples. Drizzle apples with maple syrup.
Bake apples, uncovered, for 30 minutes or until apples have softened and are cooked through. Drizzle each apple with cooking liquid before serving. Serve warm or at room temperature.