Preheat your oven to 350°F (175°C) and lightly grease a baking dish (8x8 inches works well).
In a large mixing bowl, combine the softened cream cheese, sour cream, and mayonnaise. Mix until smooth.
Stir in the minced garlic, onion powder, crushed red pepper flakes, salt, and pepper into the cream mixture.
Add the drained spinach, chopped artichoke hearts, shredded mozzarella cheese, and grated Parmesan cheese to the bowl. Mix until all ingredients are well combined.
Transfer the mixture into the prepared baking dish, spreading it evenly with a spatula.
Bake in the preheated oven for 25-30 minutes, or until the dip is hot and bubbly, and the top is slightly golden.
Once baked, remove from the oven and let it cool for a few minutes before serving.
Notes
Serve warm with tortilla chips, sliced baguette, or fresh veggie sticks. Garnish with extra Parmesan or herbs.