Preheat oven to 375°F (190°C). Bring a large pot of salted water to a boil and cook macaroni until al dente, about 7 minutes. Drain and set aside.

In a large skillet over medium-high heat, cook the ground beef, onion, and bell pepper, breaking up the meat with a spoon, until beef is no longer pink and reaches an internal temperature of 160°F (71°C) on a food thermometer, and vegetables are softened, about 6-8 minutes. Add garlic and cook 1 minute more. Drain excess fat.

Stir in the tomato sauce, diced tomatoes with their juice, Italian seasoning, smoked paprika, salt, pepper, and red pepper flakes. Simmer for 5 minutes, then mix in the cooked macaroni until evenly coated.

Transfer the mixture to a greased 9x13-inch baking dish. Cover with foil and bake for 20 minutes until bubbly.

Remove foil, sprinkle evenly with cheddar cheese, and bake uncovered for 10 minutes more, or until cheese is melted and golden. For a crispier top, broil for the final 2 minutes. Garnish with parsley.