Cook the pasta until al dente in salted water. Drain and set aside.
Prepare the sloppy joe mixture: heat butter & olive oil; sauté onion and green bell pepper until softened. Add ground beef, cook until browned; drain excess fat.
Build the sauce: stir in tomato sauce, ketchup, brown sugar, Worcestershire sauce, mustard, salt, and pepper. Simmer 5–7 minutes until sauce thickens.
Combine pasta and sauce: mix cooked pasta into the sloppy joe sauce until everything is evenly coated.
Assemble the bake: transfer mixture into a greased 9×13‑inch baking dish; sprinkle cheddar cheese evenly on top.
Bake: place in oven at 190°C (375°F) for 20–25 minutes until cheese is melted, golden, and bubbly.
Let it rest & serve: after baking, let it sit 5 minutes before slicing; garnish with parsley if desired.