01 - Preheat oven to 425°F. Line large baking sheet with parchment paper.
02 - Remove leaves and trim stem end of each cauliflower, keeping core intact. Slice each cauliflower vertically into 1-inch-thick steaks, yielding 2-3 steaks per head. Reserve remaining florets for another use.
03 - In small bowl, whisk together olive oil, cumin, smoked paprika, coriander, turmeric, garlic powder, onion powder, salt, black pepper, and cayenne until well combined.
04 - Arrange cauliflower steaks on prepared baking sheet. Brush both sides generously with spice oil mixture.
05 - Roast for 15 minutes. Carefully flip each steak, brush with remaining oil mixture, and continue roasting for 15 minutes until golden and tender.
06 - Transfer to serving platter. Garnish with fresh herbs and serve with lemon wedges.