01 - Preheat oven to 325°F. Pat brisket dry with paper towels and season all sides evenly with kosher salt and black pepper.
02 - Heat olive oil in a large Dutch oven over medium-high heat. Sear brisket on both sides until well browned, approximately 4–5 minutes per side. Remove brisket and set aside.
03 - Reduce heat to medium and add sliced onions, carrots, and celery to the pot. Sauté, stirring occasionally, until onions are caramelized and softened, about 10 minutes. Add garlic and cook for 1 additional minute.
04 - Stir in tomato paste and cook for 2 minutes. Pour in red wine, scraping the bottom of the pot to deglaze and collect browned bits. Add beef broth and Worcestershire sauce, then bring mixture to a simmer.
05 - Nestle brisket into the pot, fat side up. Add thyme, rosemary, and bay leaves. Cover with a tight-fitting lid.
06 - Transfer covered pot to the oven and braise brisket for 2½ to 3 hours, until fork-tender.
07 - Remove brisket to a cutting board and rest for 10 minutes. Skim excess fat from the cooking liquid, discard herb stems and bay leaves, then slice brisket against the grain. Spoon onion sauce over slices before serving.