01 - Preheat the oven to 425°F. Line a baking sheet with parchment paper.
02 - Remove leaves from each cauliflower head, trim the stem, and slice into 3/4-inch thick steaks. Reserve loose florets for other use.
03 - Arrange cauliflower steaks in a single layer on the prepared baking sheet. Brush both sides generously with olive oil and melted butter.
04 - Season steaks evenly with garlic powder, smoked paprika, salt, and black pepper.
05 - Roast in the oven for 20 minutes, flipping once halfway through, until golden and tender.
06 - In a mixing bowl, combine mozzarella, cheddar, and Parmesan cheeses.
07 - Remove baking sheet from the oven and evenly top each steak with the cheese mixture.
08 - Return the baking sheet to the oven and bake an additional 8 to 10 minutes, until the cheese is melted, golden, and bubbly.
09 - Sprinkle with chopped fresh parsley just before serving, if desired.