Season the roast with the salt and pepper, heat the oil in a Dutch oven and brown the meat for 5 minutes per broad side.
Transfer the roast, brown the onion wedges for 5 minutes and stir in the garlic and tomato paste for 1 minute.
Return the roast, add the broth and thyme, cover and braise at 325°F for 2 1/2 hours.
Add the carrots and potatoes, cover and continue braising for 45 to 60 minutes until the beef is at least 145°F and fork-tender and the vegetables hold their shape.
Rest the roast for 15 minutes, whisk the cornstarch and water into the simmering pot liquid and cook for 2 minutes before serving.