Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper for easy cleanup.
In a small bowl, combine the melted butter, miso paste, soy sauce, honey, garlic powder, and black pepper. Mix until smooth and well combined.
Place the cabbage wedges on the prepared baking sheet, cut side up. Brush the miso butter mixture generously over each wedge, ensuring they are well coated.
Roast in the preheated oven for 25-30 minutes, or until the cabbage is tender and the edges are golden brown.
If desired, sprinkle sesame seeds over the cabbage wedges during the last 5 minutes of roasting for added crunch.
Remove from the oven and let cool slightly. Garnish with chopped green onions before serving.