Healthy Apple Butter

Peel, core and slice the apples. Add them to a slow cooker with the cider, maple syrup, spices and salt. 2. Cook on low for 8 hours, stirring once or twice. 3. Blend until smooth, right in the slow cooker with an immersion blender or in batches in a blender. 4. Stir in the vanilla. If it's still thin, cook uncovered on high for 1 more hour. 5. Cool and store in jars in the refrigerator up to 3 weeks.