Preheat oven to 400°F.
Stir together cream cheese, Gouda, mozzarella, spinach, artichoke hearts, scallions, mayonnaise, garlic, salt, and cayenne pepper in a medium bowl until smooth.
Spoon into a 1-quart baking dish; sprinkle top evenly with Parmesan.
Bake in preheated oven until browned and bubbly, about 25 minutes.
Serve with crostini or tortilla chips.
