Apple butter is made with a combination of sliced apples and spices slow cooked until it is thick and spreadable. Because apple butter needs to be slow cooked, a crock pot allows the apples and spices to cook at the correct temperature without the chore of standing over the butter stirring while it condenses. While for canning purposes a large open kettle on the stove is still the best way, for making enough apple butter for a week or two of daily use, the crock pot is the way to go.
Wash, peel and core the apples into a large bowl.
Slice the apples into 1/4-inch slices and layer in a 5-qt. or larger crock pot.
Add the apple pie spice, sugar, salt and apple cider to the crock pot. Stir to distribute the spices over all of the apples in the pot.
Cover the crock pot and turn the temperature setting to "low."
Allow the apple butter to cook for at least 12 hours.
Remove the lid of the crock pot and turn off the heat. Allow the apple butter to cool. Transfer to an airtight container and refrigerate until needed.