Preheat oven to 425°F. Trim the base flat, careful not to cut away too much core.
Mix 2 tbsp olive oil with garlic powder, smoked paprika, salt, and pepper.
Place cauliflower in an oven-safe pot or cast iron skillet. Brush seasoned oil all over.
Cover tightly with a lid or foil. Roast 30 minutes.
Uncover, drizzle remaining oil, roast 30-40 minutes more until a skewer slides easily into the stem.
Sprinkle with parmesan and broil 3-5 minutes for extra browning, if desired.
Rest 5 minutes, slice into wedges, serve with lemon.