Melt the butter in a large pot set over medium heat. Add the chopped onion and sauté for 4–5 minutes until softened and translucent. Stir in the minced garlic and cook for an additional 30 seconds until fragrant. Pour in the crushed tomatoes and tomato sauce, seasoning with salt and pepper to taste. Blend in the brown sugar and red wine vinegar, then bring the mixture to a gentle simmer. Let the sauce cook for 10–15 minutes, stirring now and then.

Meanwhile, fill a large pot with water and bring it to a boil. Submerge the cabbage head in the boiling water and cook for 3–5 minutes, or until the leaves are flexible. Remove and gently peel off 12 large leaves.

In a large bowl, combine the ground beef, cooked rice, chopped onion, minced garlic, salt, pepper, egg, and 2 tablespoons of the chopped parsley. Mix in 1/2 cup of the prepared tomato sauce, stirring until thoroughly blended.

Lay out each cabbage leaf on a clean work surface and carefully cut a V-shaped notch at the base to remove the tough rib portion. Form about 1/3 cup of the meat mixture into a compact log and position it at the center of each leaf. Roll the leaf snugly around the filling. Repeat with the remaining leaves and filling.

Preheat the oven to 350°F. Lightly coat a 9"x13" baking dish with cooking spray. Spread half of the tomato sauce along the bottom of the prepared dish. Arrange the cabbage rolls seam-side down atop the sauce. Spoon the remaining sauce evenly over the rolls. Cover the dish tightly with foil and bake for 60–90 minutes, or until the cabbage is tender and the filling is fully cooked through.

Once baked, garnish with the remaining chopped parsley and serve warm.