3 tablespoons unsalted butter 15 cups sliced yellow onion (about 4 pounds) $ 3/4 teaspoon black pepper 1 Honeycrisp or Pink Lady apple, peeled, quartered, and cut into julienne strips 3 thyme sprigs 2 bay leaves 1/2 cup Madeira wine or dry sherry 6 cups lower-sodium beef broth $ 1/2 cup apple cider 1 tablespoon sherry vinegar 10 (1/2-ounce) slices sourdough bread, cut into 1-inch cubes 2 cups (8 ounces) grated Gruyère or Swiss cheese Thyme leaves (optional)

1. Melt butter in a Dutch oven over medium heat. Add onion to pan; cook 5 minutes, stirring frequently. Continue cooking 50 minutes or until deep golden brown, stirring occasionally. Add pepper, apple, thyme sprigs, and bay leaves; cook 3 minutes or until apples soften. Add wine; cook 2 minutes, scraping pan to loosen browned bits. Add broth and cider; bring to a boil. Reduce heat, and simmer 45 minutes. Discard bay leaves; stir in vinegar.

2. Preheat broiler.

3. Arrange bread cubes in a single layer on a jelly-roll pan; broil 2 minutes or until toasted, turning after 1 minute.

4. Preheat oven to 500°.

5. Ladle 1 cup soup into each of 10 ovenproof soup bowls. Divide the croutons evenly among bowls, and top each serving with about 3 tablespoons cheese. Place bowls on jelly-roll pan. Bake at 500° for 8 minutes or until cheese melts. Garnish with thyme leaves, if desired.