1. Core apples almost to bottom, leaving base intact. Slice off ¾-inch (2cm) wide strip of peel around hole at top; trim base to level, if necessary.
2. In bowl, combine brown sugar, dried cherries, cinnamon and nutmeg; pack into apples. Place in slow cooker. Whisk together apple cider and butter; pour over apples.
3. Cover and cook on low, basting several times, until wrinkly and very tender, about 3 to 4 hours. Transfer apples to shallow serving dish and keep warm.
4. Whisk cornstarch with 1 tbsp (15 mL) cold water; whisk into liquid in slow cooker. Cover and cook on high until sauce is thickened, about 15 minutes.
(Make-ahead: Let apples and sauce cool separately. Store at room temperature for up to 8 hours or refrigerate in airtight containers for up to 3 days. Rewarm to serve.)
5. Drizzle sauce over apples.