Heat oven to 375°F. Lightly grease a 9x13-inch baking dish.
Boil noodles in salted water until al dente. Drain well.
Warm olive oil in a large skillet over medium-high heat.
Cook onion and bell pepper until soft, about 4 minutes. Stir in garlic for 30 seconds.
Add ground beef. Cook, crumbling, until browned; drain excess fat.
Stir in tomato sauce, ketchup, tomato paste, and beef broth.
Add Worcestershire, mustard, brown sugar, chili powder, paprika, red pepper flakes, salt, and pepper.
Simmer the mixture until thickened slightly, 5 to 7 minutes.
Toss sauce with drained noodles. Fold in half the cheddar.
Spread into the dish. Sprinkle remaining cheese over the top.
Bake until bubbling and melted, 12 to 15 minutes. Rest 5 minutes.
Finish with parsley and serve warm.