NOTE! I prefer to cook overnight. You will wake to a glorious smell!
Place the apples in a slow cooker with the brown sugar, white sugar, cinnamon, ground cloves, lemon zest, cinnamon sticks, and salt. Gently toss with a large wooden spoon.
Cook on low for 10 hours until the mixture is thickened and dark brown.
Use an immersion blender and puree the apple butter. Toss in the cinnamon sticks and on low for two more hours.
Store in sterile jars for two weeks or freeze in zip lock bags for up to 6 months.