Pennsylvania Dutch Apple Butter

3 quarts sweet cider
8 pounds ripe, well-flavored apples
2 1/2 cups brown sugar, firmly packed
2 teaspoons cinnamon
1 teaspoon allspice
2 teaspoons cloves
1/2 teaspoon salt

Cook cider over high heat, uncovered, about 30 minutes or until it is reduced to half.

Wash, quarter and core unpeeled apples. Add to cider, and cook over low heat until very tender. Stir frequently. Work apple mixture through a sieve, returning the pur