Cook the rice according to package instructions and set aside. Preheat the oven to 350°F.
In a large bowl, combine the ground beef, Worcestershire sauce, egg, cooked rice, onion, parsley, garlic, salt, black pepper, dried dill, onion powder, red chili flakes if using, and ½ cup of tomato sauce.
Mix gently until everything is combined. Do not overmix.
Bring a large pot of water to a boil. Carefully add the whole head of cabbage and boil for 8 to 10 minutes, turning partway through.
Carefully remove the cabbage from the pot. Do not discard the cabbage water.
Let the cabbage cool until safe to handle. Gently remove the softened leaves and trim the thick center rib from each leaf so it rolls more easily.
If the inner leaves are still firm, return the cabbage to the boiling water for a few more minutes and continue removing leaves as they soften.
Place several cabbage leaves on the bottom of a deep 9x13-inch baking dish or roasting pan.
Place about ¼ cup of the beef and rice mixture onto each softened cabbage leaf.
Fold in the sides, roll the leaf around the filling, and place each cabbage roll seam-side down in the prepared baking dish.
Continue until the filling and usable cabbage leaves are used.
Whisk the remaining tomato sauce with ½ cup of the reserved cabbage water.
Pour the sauce evenly over the cabbage rolls.
Cover the baking dish tightly with foil.
Bake at 350°F for about 1 hour to 1 hour 15 minutes, or until the cabbage is tender and the center of the beef filling reaches 160°F on a food thermometer.
Let the rolls rest briefly, then garnish with fresh chopped dill if desired and serve with the tomato sauce from the pan.