BALSAMIC BAKED ONIONS

4 sweet onions, peeled, center slighted cored
4 TB butter
Salt
4 TB balsamic vinegar

Preheat oven to 400 degrees. Put whole onions in small baking dish that has been sprayed with Pam. On top of center of each onion but 1 TB butter, 1 TB vinegar and season with salt. Cover with foil and bake 1 hr covered with foil and then 30 minutes without the foil.