Remove beef and onions from cooker, using slotted spoon. Cut beef into slices. Skim fat from beef juices in cooker if desired. Serve beef with juices. Note: This recipe was tested in slow cookers with heating elements in the side and bottom of the cooker, not in cookers that stand only on a heated base. For slow cookers with just a heated base, follow the manufacturer’s directions for layering ingredients and choosing a temperature.