Lightly spray a 6-cup soufflé dish with cooking spray and set aside. Make a foil ring ½-inch thick for soufflé dish to sit on and place inside the bottom of a 5-quart slow cooker.
In a large bowl, combine cake mix, applesauce, eggs, pumpkin pie spice, and almond extract. Using an electric mixer, beat on low speed for 30 seconds. Scrape down sides of bowl and beat for 1 minute on medium speed. Pour into soufflé dish and set aside.
In a medium bowl, stir together baking mix, brown sugar, walnuts, cider mix, and melted butter. Sprinkle over cake batter. Use a butter knife to cut through cake and topping to swirl.
Place soufflé dish on top of foil ring in slow cooker. Place 5 folded paper towels over slow cooker bowl and secure with lid. Cook on LOW setting for 4 to 6 hours or until tester comes out clean. Do not lift lid to check cake for the first 3 hours.
Cool in soufflé dish on wire rack for 15 to 20 minutes before removing and slicing. Serve with whipped topping.