How to Make It
Heat oil in a medium nonstick skillet over medium-high. Add onions, and cook 5 minutes or until softened, stirring occasionally. Place onions in a 3-quart slow cooker. Add plums and next 6 ingredients; stir well.
Cover and cook on HIGH 3 hours or on LOW 6 hours or until fruit is tender. Spoon into jars or freezer containers; seal jars. Store in refrigerator up to 3 weeks or in freezer up to 2 months. Serve cold or at room temperature.