Preheat the oven to 350°F (175°C).

In a skillet over medium heat, cook the ground beef and onion until the beef is browned and the onion is translucent.

Drain excess fat and stir in garlic powder, salt, and pepper.

In a pot, cook the pasta according to package directions until al dente. Drain and set aside.

In a large bowl, combine the cooked beef mixture, cooked pasta, beef broth, and diced tomatoes.

Transfer the mixture to a greased casserole dish and top with shredded cheddar cheese.

Cover the dish with aluminum foil and bake for 20 minutes.

Remove the foil and bake for an additional 10 minutes, or until the cheese is bubbly and golden.