Preheat the Oven: Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish.
Cook Cauliflower: Bring a large pot of water to a boil. Cook the cauliflower florets for 3-4 minutes until tender. Drain thoroughly.
Prepare Cheese Mixture: In a medium bowl, beat together the eggs, heavy cream, salt, pepper, garlic powder, onion powder, and cheeses. Stir in the melted butter.
Assemble Casserole: Place the drained cauliflower in the prepared baking dish. Pour the cheese mixture over the cauliflower and sprinkle with the additional parmesan.
Bake: Bake for 35-40 minutes until the top is golden brown and bubbly.
Serve: Let the casserole cool slightly before serving.