Pat the boneless short ribs dry with paper towels. Trim any excessive silverskin but leave some fat for flavor. Season both sides evenly with 1 tablespoon kosher salt and the ground black pepper.

Prepare Marinade

In a bowl, combine minced garlic, brown sugar, soy sauce, Worcestershire sauce, olive oil, apple cider vinegar, smoked paprika, ground cumin, and onion powder. Stir until the sugar is mostly dissolved.

Place the seasoned ribs in a shallow dish or resealable bag and pour the marinade over them. Massage to coat thoroughly. Refrigerate and marinate for at least 1 hour, preferably 3–6 hours or up to overnight for deeper flavor. Remove from refrigerator 30 minutes before cooking to come toward room temperature.

Braising Liquid and Aromatics

Preheat and Sear

Preheat the oven to 325°F (160°C). Heat a heavy, ovenproof Dutch oven or large skillet with a tight-fitting lid over medium-high heat. Add 1 tablespoon olive oil. When shimmering, remove ribs from marinade (reserve marinade) and sear ribs in batches without crowding: 2–3 minutes per side until a deep brown crust forms. Transfer seared ribs to a plate.

Sauté Aromatics

Reduce heat to medium. Add the sliced onion, carrots, and celery to the pot. Sprinkle with the remaining 1/2 tablespoon kosher salt and sauté 4–6 minutes until softened and beginning to brown, stirring occasionally. Add the reserved marinade and tomato paste; cook 1–2 minutes, scraping browned bits from the bottom.

Deglaze and Build Braise

Pour in the red wine (if using) and simmer 1–2 minutes to reduce slightly and lift any fond. Add beef stock, bay leaf, and thyme sprigs. Return the seared ribs to the pot, nestling them into the liquid so they are at least halfway submerged (add a little extra stock or water if necessary). The liquid should come about halfway up the sides of the ribs.

Bring the liquid to a gentle simmer on the stovetop. Cover the pot with its lid and transfer to the preheated oven. Braise for 2 to 2 1/2 hours, or until the ribs are fork-tender and the meat pulls apart easily. Check at 1 1/2 hours: if liquid has evaporated too much, add 1/4 cup hot stock or water.

Finishing

Rest and Reduce Sauce

Carefully remove the pot from the oven. Transfer the ribs to a warm plate and tent with foil to rest. Place the pot on the stovetop over medium heat. Remove and discard the bay leaf and thyme stems. Skim off excess fat from the surface of the braising liquid with a spoon.

Make Pan Sauce (optional)

If you want a thicker sauce, simmer the braising liquid 6–8 minutes to reduce slightly. For a glossy thicker sauce, stir the cornstarch slurry (1 tsp cornstarch mixed with 1 tbsp cold water) to recombine, then whisk it into the simmering sauce and cook 1–2 minutes until slightly thickened. Taste and adjust seasoning with up to 1/2 teaspoon kosher salt and black pepper as needed. Whisk in 1 tablespoon butter off the heat for shine.

Serve

Return the ribs to the sauce to warm briefly (30 seconds). Spoon sauce and braised vegetables over the ribs. Sprinkle with chopped parsley and serve hot with mashed potatoes, polenta, or buttered noodles.