Preparation Steps

• Arrange a rack in center of oven; preheat to 325°. Pat beef dry with paper towels. Pulse or crush onion soup mix, pepper, and 1 Tbsp. salt until large pieces are broken down. Season beef all over with seasoning mix.
• In a large skillet over medium heat, heat 1 Tbsp. oil. Cook beef until just starting to brown, 3 to 4 minutes per side. Transfer to a plate.
• In the same skillet, heat remaining 1 Tbsp. oil. Add onions; season with remaining ½ tsp. salt. Cook, stirring occasionally, until onions start to brown, about 10 minutes. Add wine and cook until liquid is slightly reduced, 2 to 3 minutes. Pour in broth and return beef to skillet. Add thyme and bring to a simmer. Cover and transfer to oven.
• Roast beef, turning halfway through, until meat easily pulls apart with a fork, 2 hours and 45 minutes to 3 hours.
• Transfer beef to a cutting board. Remove and discard thyme. Return skillet to medium heat and bring sauce to a simmer. Cook until liquid is reduced by about half, about 15 minutes. Shred beef into large pieces and return to skillet.
• Heat broiler to high. Top skillet with cheese. Broil until cheese is melted and starting to brown in spots, about 5 minutes.
• Top with more thyme. Serve with sliced baguette alongside.