01 - Preheat the oven to 425°F and line a baking sheet with parchment paper.
02 - Remove outer leaves from each cauliflower and trim the base, leaving the core intact.
03 - Slice each cauliflower into 1-inch thick steaks; reserve any loose florets for other uses.
04 - In a small bowl, whisk together olive oil, ground turmeric, cumin, smoked paprika, coriander, cayenne pepper if using, garlic powder, sea salt, black pepper, and lemon juice until well combined.
05 - Lay cauliflower steaks on the prepared baking sheet and brush both sides evenly with the marinade.
06 - Roast in the oven for 15 minutes, then carefully flip each steak and roast an additional 12 to 15 minutes until deeply golden, tender, and crisp at the edges.
07 - Arrange the roasted cauliflower steaks on plates, sprinkle with chopped cilantro or parsley, and serve with lemon wedges.