1Make cake batter as directed on box.
2In 3 1/2- to 4-quart slow cooker, pour melted butter. Pour in cake batter (do not stir). Add cherry pie filling, pouring into center.
3Cover; cook on low heat setting 2 to 4 hours or until toothpick inserted in center comes out clean. Serve warm in bowls topped with whipped topping.