Peel, core, and slice the apples. Using a vegetable peeler, peel 1 slice of lemon peel Juice the same lemon, Prep the slow cooker with a light coat of cooking spray. Add the apples into the slow cooker, Add the cinnamon stick, the lemon peel, fresh lemon juice, and brown sugar. Stir to mix the ingredients; Set the crock pot on low. Cook for 6 hours. Stir occasionally. Remove the cinnamon stick. If you prefer a chunky apple sauce transfer to a bowl. Or transfer the mixture to a blender, blending until smooth. Set aside to cool or serve as a warm apple sauce. Store leftovers in a lidded container.