Preheat oven to 400 degrees F. Place pork ribs, in one layer, into a large shallow baking pan, meaty side up. Sprinkle with salt and pepper to taste. Bake approximately 45 minutes or until well browned. Remove from oven and spoon fat from pan; discard fat. Can be prepared ahead and refrigerated for one day. Bring to room temperature before continuing.
Reduce oven temperature to 350 degrees F.
In a small bowl, combine cornstarch with apple juice until well blended. Set aside.
In a medium saucepan over medium heat, melt butter; add onions and saute until soft. Stir in remaining apple juice, cider vinegar, brown sugar, cinnamon, and salt to taste; bring mixture to a boil. Gradually add cornstarch mixture and stir until thickened. Remove from heat and pour mixture over baked pork ribs. Cover with aluminum foil and bake an additional 60 minutes. Remove from oven.
Cut each acorn squash in half lengthwise and remove fibers and seeds; cut each into 8 wedges. Layer squash over ribs, spooning some of pan juices over them. Return to oven and bake, covered, for another 30 minutes. Add apple quarters and baste again; cover, and bake for an additional 30 minutes or until squash and apples are tender. Remove from pan, reduce liquids if desired. Serve immediately with any pan liquids served separately.
Makes 4 servings.