Cut un peeled squash into 1/4 rings with sharp knife. Remove and discard seeds. Place in shallow dish & set aside.
In 4 cup measure cook butter at High 30-45 seconds or till melted. Stir in cranberries and brown sugar. Cook, uncovered at High 2-3 min or till skins have popped, stirring once. Stir in apple; spoon in each ring.
Cover and cook at High 5-7 min or till tender. Drain juice into 1 cup measure. Dissolve cornstarch in cold water, whisk into juices. Cook at High 30-45 seconds till thickened. Pour over rings.