01 - Preheat the oven to 425°F. Line a large baking sheet with parchment paper.
02 - Remove the outer leaves and trim the stem of each cauliflower head, leaving the core intact.
03 - Place each head stem-side down and slice into 3/4-inch thick steaks, yielding 2 to 3 large steaks per cauliflower plus florets from the ends.
04 - Arrange steaks and any loose florets in a single layer on the prepared baking sheet.
05 - In a small bowl, whisk together olive oil, garlic powder, smoked paprika, black pepper, and salt.
06 - Brush both sides of the cauliflower steaks with the seasoned oil mixture.
07 - Roast for 15 minutes, then carefully flip each steak and roast for another 12 to 15 minutes until golden brown and tender.
08 - Transfer to a platter, drizzle with lemon juice, and sprinkle with parsley and pine nuts if desired. Serve warm.