Preheat the Oven: Heat the oven to 300°F (150°C) and line a large baking sheet with aluminum foil.
Prep the Ribs: Remove the membrane from the back of the ribs, if present. Place the ribs meat-side up on the foil-lined baking sheet and pat them dry with paper towels.
Mix the Dry Rub: In a small bowl, combine brown sugar, salt, pepper, paprika, garlic powder, onion powder, Italian seasoning, and cayenne pepper.
Mustard layer: Brush the ribs with Dijon mustard, making sure to coat both sides.
Season: Sprinkle the dry rub evenly over the entire surface of the ribs. Press gently to help the seasoning adhere.
Bake Covered: Wrap the ribs tightly in foil. Bake for 1½ hours.
Bake Uncovered: Remove foil and continue baking for another hour, uncovered.
Make the Sauce (optional): While the ribs bake, simmer the sauce ingredients in a saucepan over low heat until thickened, about 10 to 15 minutes
Sauce and Bake Again: Once the ribs are tender, remove them from the oven and generously brush with the BBQ sauce. Return them to the oven and bake uncovered for 20 minutes.
Broil: Switch the oven to broil. Let the ribs broil for 3-5 minutes or until caramelized. Keep a close eye to avoid burning.
Rest and Serve: Let the ribs rest for 5 to 10 minutes. Slice between the bones and serve with extra BBQ sauce and chopped green onions, if desired.