Chop the onion and measure out the ground beef, diced tomatoes, tomato sauce, elbow macaroni, and spices.
Heat a large skillet over medium heat. Add the ground beef and chopped onion. Cook until the beef is no longer pink, about 5 to 7.
Drain excess fat. Stir in diced tomatoes, tomato sauce, elbow macaroni, garlic powder, oregano, salt, pepper, and water. Bring to a gentle simmer and cover for 10.
Remove from heat, stir in 1 cup of shredded cheddar cheese until melted. Transfer to a greased 9x13-inch baking dish and sprinkle remaining cheese on top.
Preheat oven to 350°F. Bake for 20 to 25 until cheese is bubbly and golden brown. Let cool for 5 before serving.