01 - Preheat oven to 425°F. Line a large baking sheet with parchment paper.
02 - Remove leaves from cauliflower and trim stem while keeping core intact. Slice each head into 1-inch-thick steaks, yielding approximately 2-3 steaks per head.
03 - Arrange steaks on prepared baking sheet and brush both sides with olive oil. Combine cumin, smoked paprika, garlic powder, salt, and pepper in a small bowl, then sprinkle evenly over both sides of steaks.
04 - Roast for 25-30 minutes, flipping halfway through, until golden brown and fork-tender.
05 - Whisk together tahini, lemon juice, water, minced garlic, maple syrup, and salt in a bowl. Adjust consistency by adding water 1 teaspoon at a time until dressing reaches creamy, pourable consistency.
06 - Arrange roasted cauliflower steaks on serving platter. Drizzle generously with tahini dressing and garnish with parsley, toasted nuts if desired, and lemon wedges.