Preheat oven to 400°F. Line two 15x10-inch baking pans with parchment paper.
Cut cabbage into eight wedges, cutting through core and stem end, leaving core intact. Arrange wedges in prepared baking pans.
In a small bowl whisk together butter, miso, and lemon zest. Brush about half of the butter mixture over wedges.
Roast cabbage 20 minutes. Turn wedges; brush with remaining butter mixture.
Roast until cabbage is tender and edges are lightly charred, 15 to 20 minutes more.
Sprinkle with cracked black pepper. Serve with lemon wedges.
