Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper for easy cleanup.
Remove the green leaves from the cauliflower and slice the head into ¾-inch thick steaks. You should get 2-3 steaks from the central portion, with some florets that can also be roasted.
In a small bowl, whisk together the olive oil, turmeric, smoked paprika, garlic powder, salt, and black pepper until smooth.
Brush both sides of the cauliflower steaks generously with the turmeric mixture, ensuring they are well-coated. Place the steaks on the prepared baking sheet.
Roast the cauliflower in the preheated oven for 20 minutes. After 20 minutes, carefully flip the steaks and roast for an additional 15-20 minutes, until they are golden brown and tender.
Remove the cauliflower from the oven, drizzle with fresh lemon juice, and let rest for a few minutes.
Optional: While waiting, if using tahini, you can thin it with a bit of water to achieve a drizzle consistency.
Serve the cauliflower steaks warm, garnished with chopped parsley and a drizzle of tahini if desired.