This recipe for creating grilled steaks steams them first which makes them tender. The high heat roasting that follows produces seared steak with a rich flavor. This is adapted from America's Test Kitchen's Complete Plant-Based Cookbook.
Place oven rack on lowest position. Preheat oven to 500 degrees.
Working with one head of cauliflower at a time, discard outer leaves and trim stem flush with bottom florets. Halve cauliflower lengthwise through core. Cut one 1 ½ inch slab lengthwise from each half, trimming any florets not connected to the core. Repeat with remaining cauliflower. You should have at least 4 usable steaks, sometimes you can get more. If desired, you can roast some of the florets for people who may not want a whole steak.
Place steaks on a rimmed baking sheet and drizzle with 2 tablespoons of oil. Lightly sprinkle with salt and pepper and rub in to distribute. Flip steaks and repeat with remaining 2 tablespoons of oil and more salt and pepper.
Cover baking sheet tightly with foil and roast for 5 minutes. Remove foil and roast until bottoms of steaks are well browned, about 8 to 10 minutes. Carefully flip the steaks and roast for 6 to 8 minutes more or until the bottoms are nicely browned.
Transfer steaks to a platter and drizzle on the chimichurri sauce. Place the remainder of the sauce in a dish to pass.