Preheat oven to 375°F (190°C) and grease a 1-quart oven-safe baking dish.

Steam the finely chopped cauliflower for 5 minutes until fork-tender, then drain and pat dry to remove excess moisture.

In a large mixing bowl, combine the softened cream cheese, sour cream, and mayonnaise until smooth and aerated.

Fold in the prepared cauliflower, drained spinach, half of the mozzarella, and half of the parmesan cheese.

Incorporate the minced garlic, onion powder, red pepper flakes, salt, and black pepper into the mixture.

Transfer the mixture to the prepared baking dish and spread into an even layer using an offset spatula.

Distribute the remaining mozzarella and parmesan cheese across the surface.

Bake for 25 to 30 minutes or until the cheese topping is bubbly and exhibits light browning.

Rest at room temperature for 5 minutes to allow the dip to set before service.