Add butter to a skillet and melt over medium heat. Add the onions and sugar, cook for 15 minutes stirring frequently. Season with salt, pepper, and thyme. Remove from heat and set aside.
Preheat the oven to 350 degrees F. Take the rolls out of the package. Take a large knife and slice the rolls across so you have the tops and bottom separated.
Place the bottom, cut side up into a baking dish. Top with half of the cheese. Add the roast beef. Spread the onions on top. Add the remaining cheese, lastly add the tops of the rolls.
In a small bowl stir together the melted butter and onion soup mix. I like to brush this mixture on top of the rolls to make sure it’s evenly distributed.
- Add whatever toppings you want. If you love mayo and ketchup, add some.- I used provolone cheese but feel free to use cheddar cheese or mozzarella cheese.