butter-flavored vegetable cooking spray |
1 tablespoon reduced-calorie margarine |
3 medium-size sweet onions, thinly sliced |
3 cups canned no-salt-added beef broth |
1 tablespoon low-sodium worcestershire sauce |
1/4 teaspoon salt |
1/4 teaspoon pepper |
2 tablespoons dry sherry |
4 (3/4-inch-thick) slices french bread, toasted |
1/4 cup (1 ounce) shredded gruyère cheese |