In a large mixing bowl, combine the softened cream cheese, sour cream, and mayonnaise. Mix until smooth and creamy.
Add the chopped spinach, artichoke hearts, Parmesan cheese, garlic powder, onion powder, and red pepper flakes (if using) to the bowl. Stir until all ingredients are evenly incorporated.
Season the mixture with salt and pepper to taste.
Transfer the mixture into a baking dish and spread it out evenly.
Sprinkle the shredded mozzarella cheese on top.
Bake in the preheated oven for 25-30 minutes, or until the dip is bubbling and the cheese is melted and slightly golden.
Remove from the oven and let it cool for a few minutes before serving.
Notes
Serve warm with sliced baguette, tortilla chips, or vegetable sticks. Garnish with extra Parmesan or fresh herbs.