Place all ingredients in a slow cooker. Cover and cook on low for 10 hours or until apples are tender and falling apart.
Blend apples until smooth in a blender or with an immersion blender. Return to slow cooker and cook on high for 1-2 hours, until thick. Stir occasionally.
Canning instructions (optional): Bring a large pot of water to a boil. Pour apple butter into sterilized jars, making sure to wipe away any splatters from the jar rims. Leave 1/4″ of head space. Seal and boil for 15 minutes. If not canned, apple butter lasts about 1 week in the fridge.