In a large pot set over medium heat, melt the butter until foamy. Add the finely chopped onion and sauté for 4-5 minutes, or until soft and translucent. Stir in the minced garlic and cook for an additional 30 seconds until fragrant.

Pour in the crushed tomatoes and tomato sauce, stirring to combine. Season the mixture with salt and pepper, then mix in the brown sugar and red wine vinegar. Allow the sauce to come to a gentle simmer, cooking for 10-15 minutes while stirring occasionally.

While the sauce simmers, prepare the cabbage leaves. Bring a large pot of water to a boil. Submerge the entire cabbage head into the boiling water and cook for 3-5 minutes, or until the leaves are pliable. Carefully remove the cabbage and peel away 12 large, intact leaves.

In a mixing bowl, combine the ground beef, cooked rice, onion, garlic, salt, pepper, 2 tablespoons of parsley, and the egg. Add 1/2 cup of the prepared tomato sauce to the mixture and stir until well incorporated.

Lay each cabbage leaf flat on a work surface. Use a sharp knife to cut a V-shaped notch, removing the thick portion of the rib to make rolling easier. Shape about 1/3 cup of the meat mixture into a log, placing it at the center of the leaf. Roll the cabbage leaf tightly around the meat, tucking in the sides as you go. Repeat this process with the remaining cabbage leaves and filling.

Preheat your oven to 350°F (175°C). Grease a 9"x13" baking dish with cooking spray. Spread half of the tomato sauce evenly across the bottom of the dish. Arrange the cabbage rolls, seam side down, over the sauce. Pour the remaining tomato sauce over the top, ensuring the rolls are well covered.

Cover the dish with aluminum foil and bake for 60-90 minutes, or until the cabbage is tender and the meat filling is thoroughly cooked.

Remove the dish from the oven, sprinkle the rolls with the remaining parsley, and serve warm.