In a small dish, mix the melted butter with the spices (paprika, garlic powder, onion powder, salt, and red pepper flakes).
Pull and remove the outer leaves from the cabbage. Wash the cabbage and pat it dry. Carefully remove the core to expose and access the inner leaves.
Place the cabbage upside down on a large cast-iron skillet or a baking dish. Using a spoon, spread about three tablespoons of the spiced butter along the inside walls where the core used to be. It's okay if some dribbles out.
Arrange the potatoes around the cabbage and brush them with the spiced butter, reserving about 2 tablespoons of that butter for later.
Cover the whole skillet with aluminum foil, and bake at 400°F for 1 hour.
After the hour, remove the foil and flip the cabbage core-side down. Brush the cabbage with the remaining spiced butter. Return the skillet to the oven and bake for another 25 minutes, or until the cabbage has browned nicely and cooked through.
Garnish with fresh herbs, like rosemary sprigs, and serve.