01 - Set the oven to 425°F. Line a large baking sheet with parchment paper.
02 - Remove leaves and trim stems of each cauliflower, keeping the core intact. Cut each into 1-inch-thick steaks, yielding about 2-3 steaks per head. Reserve loose florets for another use.
03 - In a small bowl, combine olive oil, ground cumin, smoked paprika, garlic powder, salt, and black pepper; whisk until blended.
04 - Arrange the cauliflower steaks on the prepared baking sheet and brush both sides thoroughly with the marinade.
05 - Bake for 25 to 35 minutes, turning halfway through, until steaks are golden brown and tender when pierced with a fork.
06 - In a bowl, whisk together tahini, minced garlic, lemon juice, and salt. Gradually incorporate water while whisking until the sauce is smooth and pourable. Adjust consistency with extra water if necessary.
07 - Place roasted cauliflower steaks on a serving platter. Drizzle with tahini sauce and top with chopped parsley, toasted nuts, and pomegranate seeds if desired. Serve warm.