Preheat the oven to 350°F (175°C).

In a large skillet, brown the ground beef over medium heat until fully cooked. Drain excess fat.

Add chopped onion and bell pepper to the skillet and sauté until softened, about 5 minutes.

Stir in the diced tomatoes, cream of mushroom soup, beef broth, garlic powder, salt, and black pepper. Mix well.

In a separate pot, cook the elbow macaroni according to package instructions until al dente. Drain and add to the meat mixture.

Stir in 1 cup of shredded cheddar cheese until melted and combined.

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

Bake in the preheated oven for 20-25 minutes, or until the cheese is bubbly and golden.