Slice the apples. Keep the skins on them if you have a food mill or stick blender. This will add color and nutrients to your sauce. If you don't have either you can then peel the apples.
Dump your apple slices in your cooking vessel along with the cider and cranberries. If you are using a slow cooker, just let your apples cook until they become mush, it may take a few hours. If you are using a pressure cooker, look on your lid and bring to full pressure and then cook for just 1 minute.
Process through a food mill or use a stick blender to smooth out.