Place apples and water into a a kettle over medium heat.  Cook for 10 minutes, stirring often. Remove from heat. Cool slightly. In a crock-pot, add cooked apples, cinnamon, vanilla, salt, and sweetener. Put lid on--keeping it tilted so steam can escape. Cook on high for 6-8 hours. The time may vary depending on how juicy you apples were. Fill 8 ounce jars with hot apple butter. Add lids and rings. Place  jars in a hot water bath canner. Cover jars completely with water. Bring to a boil and process for 10 minutes. Remove jars from canner and allow to cool.  4 pints