Heat a large skillet over medium heat. Add the ground beef, diced onion, diced green bell pepper, and garlic powder. Cook, breaking the beef into small pieces, until the beef is no longer pink and the vegetables are softened, about 6–8 minutes. Drain any excess fat and return the skillet to the stove over medium heat.
Sprinkle the all-purpose flour evenly over the beef mixture. Cook and stir for 1–2 minutes, until the flour is absorbed and no raw flour smell remains.
Stir in the ketchup and Worcestershire sauce, scraping any browned bits from the bottom of the skillet.
Gradually pour in the low sodium beef broth while stirring to prevent lumps. Stir in the milk, salt, and black pepper.
Increase heat and bring the mixture to a boil. Add the dry cavatappi noodles and stir to separate them. Immediately reduce the heat to a low simmer, cover the skillet with the lid slightly ajar, and cook, stirring occasionally, until the noodles are tender, about 18 minutes.
Remove the lid and stir in the diced provolone cheese slices and the shredded mozzarella cheese until the cheeses are melted and the sauce is smooth.
Serve the skillet warm.