In a large pot, bring water to a boil and cook the cauliflower florets until tender, about 5-7 minutes. Drain well.
In a mixing bowl, combine the cooked cauliflower, cheddar cheese, parmesan cheese, sour cream, mayonnaise, minced garlic, salt, and black pepper. Mix well.
Transfer the mixture to a baking dish and spread evenly.
Bake in the preheated oven for 25-30 minutes, or until the top is golden and bubbly.