Bring a large pot of salted water to a boil. Carefully remove the core from the cabbage and place the whole head into the boiling water for about 5 minutes until the leaves are pliable.

Remove the cabbage from the pot and let it cool. Gently peel off the leaves and set aside.

In a skillet, melt half of the butter over medium heat. Add the chopped onion and cook until translucent.

In a mixing bowl, combine the cooked onion, uncooked rice, salt, and pepper. Mix well.

Take a cabbage leaf and place a spoonful of the rice mixture at the base. Roll tightly, tucking in the sides as you go. Repeat with remaining leaves and filling.

Preheat the oven to 350°F (175°C). Place the rolls seam side down in a baking dish. Pour the vegetable broth over the rolls and drizzle with the remaining melted butter.

Cover with foil and bake for 30 minutes. Remove the foil and bake for an additional 15 minutes until golden.