Bring a large pot of salted water to boil and cook your noodles. Drain and set aside.
While the noodles are cooking, heat a large skillet (12"+) over medium-high heat. Add the olive oil then the diced onion. Saute until soft.
Add the ground sirloin, Worcestershire sauce, salt, pepper, Montreal steak seasoning, and garlic. Break apart the meat and cook until no longer pink.
Add in the ketchup, mustard, diced tomatoes, and 1.5 cups of the shredded cheese. Stir together until fully combined.
Pour in the cooked noodles and stir to combine.
Sprinkle the rest of the cheese over the top, cover with a lid, and turn heat to low. Once the cheese is melted, it's ready to serve.
Notes
Optional toppings - diced dill pickles, diced onions, sauteed mushrooms, bacon - whatever you like to put on your cheeseburgers! Store leftovers covered in the fridge for up to 4 days.