Preheat oven to 350° F. In large mixer bowl, combine cake mix, eggs, applesauce and oil. Beat on medium 2 minutes, stirring occasionally. Spread half of batter in greased and floured 13x9-inch baking pan. Bake 20 minutes or until set. Top evenly with apple dip. Spoon remaining batter evenly over dip layer. Sprinkle crumb topping evenly over batter. Bake an additional 15 minutes or until set. Serve warm with whipped topping or ice cream, if desired. Store covered at room temperature. Crumb topping: In bowl, combine brown sugar, walnuts and cinnamon. Cut in butter until crumbly.