In a small bowl, combine ¼ cup of tomato sauce, 1 cup of beef broth, and 3 minced garlic cloves. Add ½ teaspoon of thyme, 1 tablespoon of Worcestershire sauce, and 1 tablespoon of white wine vinegar. Stir until well blended.
Trim any excess fat from a 2-pound chuck roast, then season all sides with 1 teaspoon of sea salt and 1 teaspoon of black pepper.
Layer half of the sliced onions (about 1 cup) at the bottom of your slow cooker. Pour half of your prepared sauce mixture over the onions.
Carefully place the seasoned chuck roast on top of the onions in the slow cooker. Follow with the remaining onions and pour the rest of the sauce mixture over the top.
Cover your slow cooker and cook on high for 4 hours or low for 7 hours until fork-tender.
To make the gravy, combine 1 tablespoon of cornstarch or all-purpose flour with each cup of sauce in a saucepan over medium heat, stirring until thickened.
Serve the French Onion Pot Roast over creamy mashed potatoes or alongside roasted vegetables, drizzling the thickened gravy over the meat, and garnish with fresh parsley.
Notes
Choose a chuck roast for maximum tenderness and flavor. Ensure proper layering in the slow cooker for optimal cooking results.