Here is the version of this comfort food classic as I remember it from my childhood: good, simple and cheesy. Some people swear it uses cheddar cheese, but I prefer mozzarella. Your choice! It is advisable to serve with with slices of white bread smeared with butter. (To be honest, I'm sure we used margarine at the time.)
Put the dry macaroni into a wide 5-quart or larger straight sided sauce pan. Add enough water just to cover the macaroni and add 1 tablespoon salt. Stir well to separate the noodles. Bring to a boil over high heat, then reduce the heat to simmer and cook until the macaroni is just shy of al dente, about 2 minutes.
While the pasta is cooking set up a strainer with a bowl underneath to capture the pasta cooking water. When the pasta is done, drain it into the strainer, reserving the starchy pasta water, rinse the macaroni briefly under cool water to stop the cooking and set it aside.
Heat the oil in the same sauce pan over medium-high heat. Add the onion and pepper and cook until the onion is translucent, about 3 minutes. Add the ground beef and break it up into large chunks. Season with the Worcestershire, tomato paste, oregano and black pepper. Cook until it turns brown, about 3 minutes more.
Add the tomatoes plus 3/4 cup of the reserved pasta water and bring to a simmer for 10 minutes. Taste for seasoning and remove from the heat.
Add the macaroni and stir gently to combine, adding additional pasta water if the sauce becomes too "tight." Stir in 1 cup of the cheese and spread into a 9 X 13-inch baking dish. (It can be prepared ahead up to this point.)
Top with the remaining cheese and reheat in a 350 degree F oven until warm and the cheese has melted.