Preheat & Prep Baking Dish: Preheat oven to 375°F (190°C). Lightly grease an 8x8-inch baking dish or a 9-inch cast-iron skillet with olive oil or butter.
Squeeze Spinach & Chop Artichokes: Make sure the thawed chopped spinach is squeezed completely dry using a clean kitchen towel or cheesecloth. Roughly chop the drained artichoke hearts into bite-sized pieces.
Mix Creamy Base: In a large mixing bowl, beat the softened cream cheese, sour cream, mayonnaise, minced garlic, lemon juice, onion powder, red pepper flakes, salt, and black pepper with a wooden spoon or hand mixer until smooth and creamy.
Fold in Greens & Cheeses: Fold in the dry spinach, chopped artichokes, 1 cup of shredded mozzarella, and ½ cup of grated parmesan cheese until evenly combined throughout the mixture.
Top & Bake: Spread the mixture evenly into the prepared baking dish or skillet. Top with the remaining ½ cup mozzarella and ¼ cup parmesan cheese. Bake uncovered for 20 to 22 minutes until hot and bubbling around the edges.
Broil & Serve: Switch oven to broil on high for 2 to 3 minutes until the cheese crust is blistered with gorgeous golden-brown spots. Let stand for 5 minutes before serving warm with toasted baguette crostini, pita chips, or crunchy vegetables.