Preheat oven to 400ºF. Line a baking sheet with foil.
Cut the cauliflower lengthwise, so they lay flat. Combine the cauliflower, olive oil, salt, garlic powder and pepper in a zip top bag. Shake until well coated. Pour onto the baking sheet and cook for 20 minutes.
Remove pan from oven and flip the cauliflower. Sprinkle parmesan cheese on top. Bake for an additional 5 to 10 minutes, or until the cauliflower is fork tender and crispy around the edges.