Cook the rice according to package instructions and let it cool slightly. Preheat your oven to 350°F (175°C).
Mix cooked rice, ground beef, Worcestershire sauce, egg, onion, parsley, garlic, salt, pepper, dill, onion powder, chili flakes (optional), and 1/2 cup tomato sauce until well combined.
Boil the whole cabbage head for 8–10 minutes, turning once. Let it cool slightly and peel off about 18 whole leaves. Reserve ½ cup of the boiling water.
Line the baking dish with extra cabbage leaves. Fill each leaf with about 1/4 cup of filling, roll tightly, and place seam-side down. Pack rolls snugly in rows.
Mix remaining tomato sauce with reserved cabbage water. Pour evenly over the cabbage rolls.
Cover with foil and bake for 1.5 hours. Uncover for the last 10–15 minutes for light browning.
Let rest for 5–10 minutes. Garnish with fresh dill if desired and serve warm.