01 - Preheat the oven to 425°F. Line a large baking sheet with parchment paper.
02 - Remove outer leaves from the cauliflower heads while keeping the stems intact. Slice each head vertically into 1-inch-thick steaks, reserving extra florets for another use.
03 - Arrange the cauliflower steaks on the prepared baking sheet. Brush both sides with olive oil and season evenly with ground cumin, smoked paprika, garlic powder, salt, and freshly ground black pepper.
04 - Roast for 25 to 30 minutes, flipping the steaks halfway through, until golden brown and tender.
05 - Whisk tahini, fresh lemon juice, minced garlic, and salt in a bowl. Gradually add cold water, one tablespoon at a time, whisking until the sauce achieves a creamy and pourable texture.
06 - Place the roasted cauliflower steaks on a serving platter. Drizzle generously with tahini sauce, sprinkle with chopped parsley and toasted nuts if using, and serve with lemon wedges.