01 - Preheat oven to 425°F. Line a baking sheet with parchment paper.
02 - Remove leaves and trim stem from cauliflower, keeping core intact. Cut each head into ¾-inch thick steaks, reserving leftover florets for another use.
03 - Place cauliflower steaks on baking sheet. Brush both sides with olive oil; season with sea salt, black pepper, and smoked paprika if using.
04 - Roast for 20 minutes, then carefully flip steaks and roast an additional 10 minutes until golden and tender.
05 - In a bowl, combine parsley, cilantro, red wine vinegar, garlic, red pepper flakes, sea salt, and black pepper. Stir in extra-virgin olive oil until fully incorporated.
06 - Arrange roasted cauliflower steaks on a platter and spoon chimichurri sauce generously on top. Serve warm or at room temperature.