Preheat your oven to 350°F (175°C).
In a mixing bowl, combine the cream cheese, sour cream, and mayonnaise until smooth.
Add the chopped spinach, mozzarella, and Parmesan cheese to the mixture.
Stir in the minced garlic and onion powder.
Season with salt and pepper to taste.
Transfer the mixture to a baking dish and spread it evenly.
Bake for 20 minutes or until bubbly and golden on top.
Remove from the oven and let it cool slightly.
Serve warm with tortilla chips or fresh veggies.