Preheat outdoor grill to medium heat.
Cut the cauliflower into “steaks” - remove the leaves from the base (do NOT remove core) of the cauliflower and cut the cauliflower into 4 steaks that are each 1/2 inch thick.
In a small bowl, combine spices (salt and pepper through garlic powder). Brush each cauliflower steak generously with olive oil, then season evenly with spice mixture.
Place cauliflower on grill, and cook for 4 to 6 minutes per side or until cooked through.
In a food processor combine all of the ingredients for the chimichurri and blend until smooth.
Serve the cauliflower with the chimichurri drizzled on top.