Remove outer leaves from the cauliflower head. Resting cauliflower on stem, cut in half from top to bottom, separating the stem in half. Trim off outer rounded edge of each piece to create 1” thick steaks.
Place cauliflower steaks and any other extra pieces on a baking sheet. Drizzle with olive oil and sprinkle with salt, garlic powder, paprika. Roast until stems are tender when pierced with a fork, about 30 minutes. Top roasted cauliflower steaks with walnut-kale pesto and enjoy!