Preheat the oven to 400°F with a rack in the center position.
Remove the outer leaves from the cauliflower and trim the stem so the cauliflower rests flat. Place the cauliflower stem side down then slice vertically into 1-inch-thick steaks.
Place the cauliflower steaks on a sheet pan. Drizzle with the olive oil and sprinkle with the salt, garlic powder, and paprika. Roast until the stems are fork tender, about 30 minutes.