Preheat oven to 450 degrees F (230 degrees C). Line a baking sheet with aluminum foil.
Place the cauliflower onto a cutting board with the stem side facing upwards; cut vertically into 4 steaks approximately even in thickness. Arrange 'steaks' onto the prepared baking sheet. Drizzle olive oil over the steaks; season with garlic powder, salt, and black pepper.
Roast in preheated oven for 20 minutes, turn with a spatula, and continue to roast until soft in the middle and darkening around the edges, about 15 minutes more.