Ingredients

• 5 pounds boneless beef chuck roast
• Kosher salt, freshly ground pepper
• 1/4 cup olive oil
• 2 large onions, sliced
• 2 cups dry red wine
• 1/2 cup red wine vinegar
• 1/4 cup sugar
• 2 garlic cloves, crushed
• 4 cups low-sodium chicken broth
• 1 bunch thyme
• 1/4 small red onion, finely chopped
• 2 tablespoons red wine vinegar
• 1 red jalapeño or Fresno chile, with seeds, finely chopped
• 1/4 cup chopped fresh basil
• 1/4 cup chopped fresh chives
• 1/4 cup chopped fresh flat-leaf parsley
• 1/4 cup finely grated lemon zest
• Kosher salt, freshly ground pepper
• 2 tablespoons red wine vinegar
• Kosher salt, freshly ground pepper
• 1 cup all-purpose flour
• 1/4 cup vegetable oil

Instructions

1. Preheat oven to 325°F. Tie roast with kitchen twine at 1" intervals; season with salt and pepper.
2. Heat oil in a large ovenproof pot over medium-high heat. Cook onions, stirring occasionally, until soft, 10–15 minutes. Add wine, vinegar, and sugar. Bring to a boil, reduce heat, and simmer until reduced by half, 10–12 minutes. Add garlic and broth and return to a simmer; add roast and thyme. Cover and braise in oven, turning roast occasionally, until roast is tender, 2 1/2–3 hours.
3. Transfer roast to a large baking dish and strain braising liquid over. Cover and chill onions. Cover roast at least 12 hours.
4. DO AHEAD: Roast can be braised 2 days ahead. Keep chilled.
5. Combine onion and vinegar in a medium bowl. Let sit 30 minutes; drain. Add chile, basil, chives, parsley, and lemon zest and toss; season with salt and pepper.
6. Scrape fat from beef; discard. Transfer beef to a cutting board. Bring solidified braising liquid to a boil in a large saucepan. Reduce heat and simmer, stirring occasionally, until reduced to 2 cups, 25–30 minutes. Add vinegar and braised onions; season sauce with salt and pepper.
7. Place flour in a shallow bowl. Remove twine from roast and slice into eight 1–1 1/2" pieces; season with salt and pepper. Heat oil in a large nonstick skillet over medium heat. Working in batches, dredge meat in flour and cook until browned and crisp, about 4 minutes per side. Arrange on a platter and drizzle with sauce; top with gremolata.