Start by mixing the chopped onion, bell pepper, garlic, Worcestershire sauce, wine, bay leaves, salt, and pepper in a bowl. Add the beef roast and let it soak in this flavorful blend for at least 24 hours in the fridge. This long marination infuses the meat with depth and helps tenderize it.
In a large, heavy pot over medium heat, warm the oil. Remove the beef from the marinade and sear it until browned on all sides. Once it's browned, remove it from the pot. Add the sugar to the same pot and let it melt and caramelize until it reaches a rich dark brown — but be careful not to burn it.
Pour in the marinade and stir well, letting it simmer briefly to bring the flavors together. Return the beef to the pot, nestling it into the mixture.
Lower the heat, cover, and let the dish simmer gently for 2.5 to 3 hours, turning the roast occasionally so it cooks evenly. The sauce should reduce and thicken as it cooks, coating the meat in a luscious, almost syrupy glaze. Alternatively, you can cook it in a 160°C (325°F) oven or in a slow cooker on low for 6–8 hours.
Once fully cooked, remove the beef and let it rest briefly. Slice into medallions and serve generously coated with the sauce.