Caramelized sweet onions plus a low-and-slow braise turn beef brisket into an irresistibly tender and flavorful main dish.
1. Preheat oven to 325°F. Halve each onion and thinly slice. Trim the brisket of excess fat. Season with salt and pepper. In a 12-inch skillet, heat the oil on high. Add brisket and cook 4–5 min. per side, until browned. Transfer to a roasting pan.
2. Reduce heat under same skillet to medium. Add onions and sugar to skillet. Season with salt and pepper. Cook 10 min., until onions are golden, stirring occasionally.
3. Into skillet, stir the flour and tomato paste. Cook 30 sec. Add the broth, red wine, and thyme. Heat to a boil, then remove from heat.
4. Carefully pour onion mixture over brisket and tightly cover pan with foil. Cook 3–4 hours, until fork-tender.
5. Remove from oven and let rest 15 min. Discard thyme sprigs. Slice brisket against the grain and serve with onions and cooking liquid.
Garnish with finely chopped parsley for a pop of freshness.