Preheat oven to 350. Prepare a 9" square pan with cooking spray; set aside. In a large saucepan, heat applesauce until boiling; add oats and raisins; set aside. In a mixing bowl, combine flour, brown sugar, walnuts, margarine, egg, vanilla extract, baking powder, baking soda, cinnamon, and salt. Mix well. Add applesauce mixture and mix until all is moistened. Pour batter into prepared pan. Sprinkle granulated sugar evenly over top. Bake for 40 minutes, or until toothpick inserted in center comes out clean.