Pat the beef chuck roast dry with paper towels and season generously with salt and black pepper.

In a large Dutch oven, heat olive oil over medium-high heat and sear the beef roast on each side for about 4-5 minutes.

Remove the beef and sauté the chopped onion in the same pot for 4-5 minutes until softened.

Stir in minced garlic and cook for an additional minute.

Pour in balsamic vinegar to deglaze the pot, scraping up browned bits from the bottom.

Add beef broth and brown sugar, stirring to combine, then return the beef to the Dutch oven.

Scatter cranberries and thyme around the beef and add optional carrots if using.

Cover the Dutch oven and braise in a preheated oven at 325°F for 3 to 3.5 hours.

Remove the roast from the oven and let it rest for 10 minutes.

Skim excess fat from the sauce and simmer to thicken if desired.