Preheat oven to 350 degrees F. Use a serrated knife to slice the rolls in half. Place the bottom layer on a baking sheet and cover it with 4 slices of cheese.
Heat some oil in a large skillet over medium-high heat. Add the beef and brown it completely. Once the beef is browned, stir in the onions and red bell peppers and cook for 1-2 minutes. Stir in the garlic and tomato paste. Cook for 30 seconds.
Add the ketchup, mustard, garlic powder, chili powder, Worcestershire sauce, water, salt, pepper, and cook for 25 minutes over medium-high heat, uncovered, stirring occasionally.
Once the 25 minutes are up, check for seasoning.
Pour the beef mixture all over the sandwiches, you don't have to use all of the beef! You can leave some behind.
Top the beef with the remaining cheese and bread. Brush the buns with melted butter and top it off with sesame seeds.
Bake for 10 minutes and enjoy!