01 - Preheat the oven to 425°F. Line a large baking sheet with parchment paper.
02 - Remove leaves and trim the base of each cauliflower head, keeping the core intact. Cut each head into 1-inch thick steaks, yielding 2–3 steaks per head. Reserve loose florets for another use.
03 - Place cauliflower steaks on the prepared baking sheet. In a small bowl, combine olive oil, cumin, smoked paprika, garlic powder, salt, and black pepper. Brush both sides of the steaks with this mixture.
04 - Roast in the oven for 20 minutes, flipping halfway through, until the steaks are golden and tender.
05 - While roasting, mix harissa paste, lemon juice, and maple syrup (or honey) in a small bowl.
06 - Remove cauliflower from the oven and brush generously with the harissa glaze. Return to oven and bake for an additional 5 to 7 minutes until caramelized.
07 - Transfer cauliflower steaks to plates, garnish with chopped parsley, and serve immediately.