Slice the cabbage. Preheat the oven to 400°F (200°C). Cut the bottom off the cabbage and stand it upright so that the flat end is on the cutting board. Cut the cabbage into 1-inch thick slices.
Arrange on a baking sheet and season. Place the cabbage steaks in a single layer on a baking sheet. Brush the oil on both sides of the cabbage steaks and evenly sprinkle both sides with garlic powder, salt, and pepper.
Cook until tender. Roast the cabbage steaks for 40 to 45 minutes, rotating the pan halfway through, until the edges are crispy and the center is tender.
