1Heat oven to 500°F. Heat 12-inch skillet over high heat. Spray onion with cooking spray; add to skillet. Stir in 1/2 teaspoon of the herb blend. Cook 11 to 12 minutes, stirring frequently and adding water 2 tablespoons at a time, until onion is golden brown.
2Meanwhile, in 2-quart saucepan, heat broth and remaining 1 1/2 teaspoons herb blend over medium heat until hot. Remove from heat; add beef, pushing beef down into liquid until covered. Let stand 5 minutes.
3Place buns, cut sides up, on ungreased cookie sheet. Bake 4 minutes or until lightly toasted.
4Remove beef from broth; reserve broth. On bun bottoms, place beef, onion and cheese; cover with bun tops. Serve with warm broth for dipping.