In a medium bowl, add 2 cups of water and 3 beef bouillon cubes. Microwave on high for 4 to 5 minutes, or until the beef bouillon cubes are dissolved. Set aside.
In a large saucepan, cook ground beef over medium-high heat until no longer pink. Drain grease and return beef to the pan.
Turn heat down to medium and add the chopped onion, salt, pepper, minced garlic, Italian seasoning, garlic powder, and chili powder. Stir well and let it cook until onions are soft and translucent, about 5 to 7 minutes
Add Worcestershire sauce, tomato paste, and diced tomatoes (in their juices) and stir together.
Add the dried large elbow macaroni noodles and beef bouillon broth to the beef mixture and stir together.
Cover and let simmer over medium-low heat for 5 minutes. Uncover and stir. Cover again and let cook for another 5 minutes, or until the pasta is done.
Stir in the sour cream and milk.
Pour half of the beef and pasta mixture into a 9x13 glass baking dish. Sprinkle half of the mozzarella and cheddar cheese over the casserole
Pour the remaining mixture into the dish and spread evenly. Sprinkle the remaining half of the mozzarella and cheddar cheese over the top of the casserole.
Bake uncovered at 400°F for 10 minutes, or until the sides of the casserole are bubbling.