Roast the cauliflower steaks, turning once, until the cauliflower is tender and golden, about 25-30 minutes. Remove from the oven and top each cauliflower steak with marinara sauce. Sprinkle with shredded mozzarella cheese and freshly grated parmesan cheese. Switch the oven to broil and cook the cauliflower until the cheese is bubbly and golden in spots, about 3 minutes. Serve with more grated parmesan cheese and fresh basil.