Preheat oven to 350 degrees Fahrenheit.
Cut the cauliflower into smaller florets. Discard the stack and the other leaves.
Bring a pot of water to a boil. Add the cauliflower florets to the pot. Cook until you can insert a knife into a piece without much resistance. It should be tender but still somewhat crunchy; not mushy.
Drain the cauliflower. Get rid of as much extra moisture as possible. Spread the cauliflower into a small casserole dish.
In a bowl, beat the eggs until fluffy.
Stir the cream into the eggs.
Add the melted butter to the eggs.
Add the salt, pepper, celery salt, and onion powder to the egg mixture.
Stir the white cheddar, parmesan, and mozzarella cheeses into the egg mixture.
Pour the egg mixture over the cauliflower.
Bake in a preheated oven for about 45 minutes.