French Dip Bundtwich with Caramelized Onions

Heat oven to 350°F. Line 15x10x1-inch pan with foil; set aside. Spray 12-cup fluted tube cake pan with cooking spray.

Remove dough from both cans; do not unroll. Roll outsides of dough in sesame seed. Place in pan in a circle; pinch ends together to seal into 1 ring. Bake 35 to 40 minutes or until golden brown. Cool slightly, about 10 minutes. Remove bread from pan to cooling rack. Cool completely, about 1 hour.

In 12-inch nonstick skillet, melt butter over medium-high heat. Add onions, thyme and salt. Cook 10 to 15 minutes, stirring frequently, until starting to brown. Stir in 1/4 cup of the beef broth; continue to cook 3 to 5 minutes or until liquid is absorbed and onions are browned and tender. Remove onion mixture to small bowl. Add 1/2 cup of the broth and the roast beef to skillet. Heat to simmering over medium heat 3 to 5 minutes or until roast beef is heated through.

With serrated knife, carefully cut bread in half horizontally. Pinch or tear bread from cut sides of top and bottom halves, leaving about a 3/4-inch shell; discard or save bread pieces for another use. Place top half of bread, cut side up, on foil-lined pan; top with half of the mozzarella slices, the roast beef, onion mixture and remaining mozzarella slices.

Bake 8 to 10 minutes or until cheese is melted; place remaining half of bread onto sandwich and continue baking 5 minutes.

Meanwhile, add remaining 2 cups broth to broth remaining in skillet. Heat over medium-high heat 2 to 3 minutes or until heated through. Transfer broth to serving dish. To serve, cut sandwich into 8 wedges; serve with heated broth.