01 - Set oven to 425°F and line a large baking sheet with parchment paper.
02 - Remove leaves and trim base from cauliflower heads, keeping cores intact, then slice each into 1-inch thick steaks.
03 - Place cauliflower steaks flat on the prepared baking sheet.
04 - Whisk olive oil, cumin, smoked paprika, garlic powder, salt, and black pepper; brush mixture onto both sides of the steaks.
05 - Bake for 20 minutes, flipping halfway until golden and tender.
06 - Combine harissa paste, lemon juice, and maple syrup (or honey) in a small bowl.
07 - Brush harissa glaze over steaks and return to oven for 5 to 7 minutes to caramelize.
08 - Transfer to plates, sprinkle with chopped parsley, and serve immediately.