Preheat oven to 425 degrees F, spray a baking sheet with cooking spray, set aside.
Clean the cauliflower heads, keeping the core together slice the cauliflower into thick steaks, you should get 3-4 per head. Lay the steaks out in a single layer on the baking sheet. Drizzle each steak with olive oil and lemon juice, season with salt and pepper,
Roast the cauliflower steaks for 15-20 minutes until tender. Keep the oven on a toast the pepitas until they are golden brown, 5-6 minutes.
In a small bowl combine the olive oil, red pepper flakes, chili powder and parsley. Once the steaks are done drizzle with the oil mixture, sprinkle with the toasted pepitas and crumbled feta.