Preheat oven to 400°F (200°C).
Place the cauliflower slices on a baking sheet and brush both sides with olive oil. Season with salt and pepper.
Roast for 20-25 minutes, flipping halfway, until tender and lightly browned.
In a small bowl, combine the parsley, garlic, and lemon zest to make the gremolata.
Serve the roasted cauliflower steaks warm, topped with the gremolata.
