Sauté the onion: In a large pot or Dutch oven, heat olive oil over medium heat. Add the diced onion and cook until soft and translucent, about 4–5 minutes.
Brown the ground beef: Add the ground beef and cook until fully browned, breaking it up with a spoon as it cooks. Drain excess fat if needed.
Season the mixture: Stir in the salt, black pepper, Italian seasoning, garlic powder, and oregano. Mix well to evenly distribute the seasonings.
Add tomatoes and pasta: Pour in the petite diced tomatoes (with their juices), tomato sauce, beef broth, and uncooked macaroni. Stir to combine.
Simmer: Bring the mixture to a boil, then cover the pot. Reduce heat to medium-low and simmer for 10–13 minutes, or until the pasta is tender and most of the liquid has been absorbed. Stir occasionally to prevent sticking.
Finish and serve: Taste and adjust seasoning if needed. If using, stir in shredded cheddar cheese until melted. Garnish with green onions or parsley and serve warm.