Pat the brisket dry with paper towels. Trim any excessive hard fat, leaving about 1/8–1/4 inch of fat cap for flavor and moisture. Rub the entire surface with the kosher salt and coarse black pepper, pressing to adhere.

Apply dry rub

Combine all Dry Rub ingredients (paprika, brown sugar, garlic powder, onion powder, cumin, mustard powder, red pepper flakes) in a small bowl. Massage the rub evenly over all sides of the brisket so it forms a uniform coating. Cover and refrigerate for at least 2 hours or up to overnight to let flavors penetrate; bring to room temperature for 30–60 minutes before cooking.

Sear and Aromatics

Preheat oven to 300°F (150°C). In a large Dutch oven or heavy ovenproof pot, heat 2 tablespoons neutral oil over medium-high heat until shimmering. Sear the brisket fat-side down first for 4–6 minutes until well browned, then flip and brown the other side 4–6 minutes. Remove brisket to a plate and reduce heat to medium.

Add the sliced onion, carrots, celery, and smashed garlic to the pot. Cook, stirring occasionally, until the onions begin to brown and soften, 5–7 minutes. Stir in the Worcestershire sauce and apple cider vinegar to deglaze the pan, scraping up browned bits from the bottom with a wooden spoon.

Braise

Add the beef stock and red wine to the pot and bring to a low simmer. Add the bay leaves. Return the brisket to the pot, fat side up, nestling it on top of the aromatics. The liquid should come about one-third to half up the sides of the brisket; if needed, add a little more stock or water to reach that level.

Cover the pot with a tight-fitting lid and transfer to the preheated oven. Braise until the brisket is fork-tender and an instant-read thermometer inserted into the thickest part reads about 200–205°F (93–96°C), about 3 to 4 hours for a 4 lb brisket. Check once midway and baste the top with the braising liquid if the exposed meat looks dry.

Rest and Finish

Carefully transfer the brisket to a cutting board and tent loosely with foil. Let it rest for at least 30 minutes (45–60 minutes if time allows). This rest lets juices redistribute and makes slicing easier.

While the brisket rests, skim fat from the surface of the braising liquid and strain the liquid into a saucepan. Reduce the strained liquid over medium-high heat until slightly thickened, about 8–12 minutes. Whisk in the butter, if using, to add gloss and richness and adjust seasoning with salt and pepper to taste. Chop the reserved cooked aromatics or purée a portion into the sauce for a thicker gravy (optional).

Slice the brisket against the grain into thin slices. Serve slices topped with the reduced braising sauce and sprinkle with chopped parsley if desired.