- In a medium skillet over medium heat, melt 2 tablespoons of butter and cook the onions until lightly browned and soft. Set aside. 
- Preheat the oven to 350°F and grease a 9 x 13 baking dish with nonstick cooking spray. 
- Keeping the Hawaiian sweet rolls attached, run a serrated knife through the middle of the loaf, dividing the top and bottom halves. 
- Place the bottom half in the prepared baking dish and evenly lay on the cheese. 
- Scatter on the roast beef, followed by the onions. 
- Top with the top half of the rolls. 
- In a small bowl, melt the remaining 8 tablespoons of butter in the microwave (about 15 seconds). Stir in the Au Jus gravy mix, Worcestershire sauce, sesame seeds, garlic powder, and onion powder. 
- Pour sauce over the rolls and bake until the cheese has melted, about 15-20 minutes.