Sear the roast: Pat chuck roast dry and season with ½ teaspoon salt and pepper. Heat 1 tablespoon olive oil in Dutch oven over medium-high heat. Sear roast 5 minutes per side until deep brown crust forms. Remove and set aside.
Caramelize onions: Add remaining 2 tablespoons oil to pot. Add onions with ½ teaspoon salt and ¼ teaspoon pepper. Cook on medium heat 5 minutes, then reduce to medium-low and cook 20-25 minutes until golden and soft.
Build the sauce: Stir in garlic and maple syrup. Cook 7-8 minutes. Sprinkle flour over onions and stir 1 minute. Pour in wine and scrape bottom of pot. Add beef broth, rosemary, and bay leaf. Bring to simmer.
Braise the roast: Return roast to pot, nestling into onions. Liquid should mostly cover meat. Cover with lid and transfer to 300°F oven. Braise 3 hours.
Finish cooking: After 3 hours, flip roast and gently pull apart with forks. Re-cover and cook 30-45 minutes more until meat shreds easily.
Rest and serve: Remove rosemary and bay leaf. Let rest 10 minutes before serving with onion gravy spooned over top.
