Preheat your oven to 425°F. Line a baking sheet with parchment paper.
Remove the outer leaves of the cabbage and slice each head into 1-inch thick steaks. You should get about 4-6 steaks from each cabbage.
In a small bowl, mix together the olive oil, garlic powder, onion powder, salt, and black pepper.
Brush both sides of each cabbage steak generously with the olive oil mixture. Place the steaks on the prepared baking sheet.
Sprinkle the grated Parmesan cheese evenly over the top of each cabbage steak.
Roast in the preheated oven for 25-30 minutes, flipping halfway through, until the edges are crispy and the cabbage is tender.
Remove from the oven and garnish with chopped parsley before serving.