Preheat your oven to 475°F. Adjust the oven rack to the middle position. Lightly spray a 13x9-inch baking dish with cooking oil spray. Spread the uncooked elbow pasta evenly across the baking dish.

In a bowl, break the ground beef into small pieces, about ½-inch size. Season the beef with a bit of salt and pepper, then sprinkle it over the pasta in the dish.

Mix together the water, tomato sauce, Worcestershire sauce, mustard powder, brown sugar, garlic powder, chopped pickles, and a bit of salt and pepper. Pour this mixture over the pasta and beef, then stir gently to combine. Cover the dish tightly with aluminum foil and bake for 25 minutes.

While the pasta bakes, cook the bacon in the microwave on a plate for about 5 minutes, until crispy. Set the bacon aside on a paper towel-lined plate to absorb any extra grease, then crumble it into small pieces.

After 25 minutes, take the dish out of the oven. Stir the pasta to make sure nothing is sticking to the sides or bottom of the pan. Lay the slices of American cheese over the top and sprinkle the crumbled bacon on top of the cheese. Return the dish to the oven, uncovered, and bake for another 5-8 minutes, until the pasta is tender and the cheese is fully melted.

Let the dish cool for about 10 minutes before serving. If you're using onions, sprinkle them over the top right before serving.