Preheat oven to 350°F. Spray a small baking dish with cooking spray and set aside.

Drain the can of artichoke hearts, squeeze out any excess liquid, and roughly chop them. Thaw the frozen spinach and squeeze out as much liquid as possible.

In a large bowl, combine the softened cream cheese, mayonnaise, sour cream, and the finely minced garlic. Stir or beat until smooth and fully combined, scraping the sides of the bowl as needed.

Add ½ cup grated mozzarella and ½ cup freshly grated Parmesan to the bowl, then add the chopped artichoke hearts, drained spinach, and the optional pinch of red pepper flakes and/or lemon zest. Stir until the mixture is evenly combined.

Transfer the mixture to the prepared baking dish and spread it into an even layer. Sprinkle the top with the extra grated mozzarella and extra grated Parmesan to your liking.

Bake for 20–25 minutes, until the dip is bubbly and the top is beginning to brown. If you want more browning, place the dish under the broiler for 1–2 minutes—watch very closely to prevent burning.

Remove from the oven, let sit for a few minutes, then serve immediately with tortilla chips, vegetable sticks, crackers, or toasted bread.