Preheat your oven to 375°F (190°C).

In a mixing bowl, combine the cream cheese, sour cream, and mayonnaise until smooth and well combined.

Add the spinach, artichoke hearts, mozzarella cheese, Parmesan cheese, garlic, onion powder, black pepper, and salt to the bowl. Mix until all the ingredients are fully incorporated.

Transfer the mixture to a baking dish and spread it evenly.

Bake in the preheated oven for 20-25 minutes, or until the dip is hot and bubbly, and the top is lightly golden.

Remove from the oven and let the dip cool for 5 minutes before serving.

Serve warm with tortilla chips, pita bread, or vegetable sticks for dipping.