In a large mixing bowl, combine the cream cheese, sour cream, and mayonnaise. Stir until smooth and well combined.
Add the Parmesan cheese, mozzarella cheese, spinach, artichoke hearts, minced garlic, red pepper flakes, black pepper, and salt. Mix until all ingredients are incorporated.
Transfer the mixture into a baking dish and smooth the top with a spatula.
Bake for 20-25 minutes, or until the top is bubbly and golden brown.
Remove from the oven and let it rest for a few minutes before serving. Serve with baked pita chips.
Notes
You can make this dip ahead of time and bake it just before serving for maximum flavor.