Prep the oven: Preheat to 375°F (190°C). Lightly grease a small baking dish (about 1.5–2 quarts) with olive oil or butter.
Drain the spinach well: Thaw the spinach, then squeeze out excess moisture using your hands or a clean kitchen towel. Too much liquid dilutes the dip.
Chop the artichokes: Drain them thoroughly and rough-chop so there are plenty of chunky bites.
Mix the base: In a large bowl, combine cream cheese, sour cream, and mayonnaise.
Beat until smooth. Stir in garlic, lemon zest, lemon juice (if using), red pepper flakes, salt, and pepper.
Add the greens and cheese: Fold in spinach, artichokes, 3/4 cup mozzarella, and all the Parmesan. Taste and adjust seasoning.
Assemble: Spread the mixture evenly in the baking dish.
Sprinkle the remaining mozzarella (and a little extra Parmesan if you like) on top.
Bake: Cook for 20–25 minutes, until the edges bubble and the top turns lightly golden. For a deeper color, broil for 1–2 minutes at the end—watch closely.
Rest and serve: Let it sit for 5 minutes to set slightly. Serve warm with your favorite low-carb dippers.