DELICIOUS! This is by far a wonderful sandwich when you are craving onions, melting cheese and steak! Very EASY preparation. Provolone cheese is the only kind to use in making this sandwich. I have used thinly sliced ribeye steak with success, but have listed deli roast beef in this recipe. We prefer mayonnaise and mustard as condiments to this sandwich which enhance the flavor. Note: In my area we have a restaurant named J. Michael's Philly Deli. This recipe is similar to his version and it's darn good!