Place the apples in a crock-pot with the heat turned on high. In a separate bowl, combine your agave syrup, cinnamon, cloves, nutmeg and salt. Pour the mixture over the apples and mix well to coat everything. Cover and cook for 1 hour.
Reduce heat to low and continue cooking for approximately 8 to 9 hours, stirring occasionally, until the mixture is dark brown and nicely thickened. Remove the cover and cook on low for about another hour.
Place your apple butter into airtight containers and store in the refrigerator or freezer. Yields three 10 oz. containers.
For a smoother texture, stir apple butter with wire whisk before storing.