Prepare the Tomato Sauce: Melt the butter in a large pot over medium heat.Add the finely chopped onion and cook for 4–5 minutes, or until the onion becomes translucent. Add the Garlic: Stir in the minced garlic and cook for 30 seconds.
Build the Sauce: Add the undrained crushed tomatoes, tomato sauce, salt, and pepper. Stir in the brown sugar and red wine vinegar until combined.
Simmer the Sauce: Bring the sauce to a gentle simmer. Cook for 10–15 minutes, stirring occasionally.
Boil the Cabbage: While the sauce simmers, bring a large pot of water to a boil. Carefully immerse the whole cabbage head in the boiling water and cook for 3–5 minutes, or until the leaves become pliable. Separate the Leaves: Remove the cabbage from the water and carefully peel away 12 large leaves.
Prepare the Filling: In a large bowl, combine the ground beef, cooked rice, finely chopped onion, minced garlic, salt, pepper, 2 tablespoons of the chopped parsley, and the egg. Add 1/2 cup of the prepared tomato sauce and stir until everything is evenly combined. Trim the Cabbage Leaves: Lay each cabbage leaf flat on a work surface. Using a small knife, cut a V-shaped notch around the thick portion of the cabbage rib to remove it.
Fill the Cabbage Rolls: Shape approximately 1/3 cup of the meat mixture into a log shape and place it in the center of a cabbage leaf.
Roll the Cabbage: Fold and roll the cabbage leaf around the filling to enclose it. Repeat with the remaining filling and cabbage leaves. Preheat the Oven: Preheat the oven to 350°F.
Prepare the Baking Dish: Coat a 9 x 13-inch baking dish with cooking spray. Spread half of the tomato sauce evenly across the bottom of the dish. Arrange the Cabbage Rolls: Place the cabbage rolls seam-side down in the baking dish.
Add the Remaining Sauce: Spoon the remaining tomato sauce over the cabbage rolls.
Bake the Cabbage Rolls: Cover the baking dish with foil and bake for 60–90 minutes, or until the cabbage is tender and the meat is cooked through.
Garnish and Serve: Remove the cabbage rolls from the oven and sprinkle with the remaining 2 tablespoons of chopped fresh parsley. Serve warm.