01 - Preheat oven to 425°F. Line a large baking sheet with parchment paper.
02 - Remove outer leaves from cauliflower heads and trim stem while keeping core intact.
03 - Place each cauliflower stem-side down and cut into 3/4 to 1-inch thick steaks using a large knife. Reserve any florets that break off.
04 - In a small bowl, whisk together harissa paste, olive oil, lemon juice, garlic, ground cumin, smoked paprika, sea salt, and black pepper.
05 - Arrange cauliflower steaks on the prepared baking sheet and brush both sides generously with the harissa marinade.
06 - Roast for 30 to 35 minutes, flipping halfway through, until steaks are golden, tender, and slightly charred at the edges.
07 - Transfer steaks to plates. Sprinkle with chopped parsley and toasted slivered almonds. Serve with lemon wedges.