Adjust oven rack to middle position and preheat oven to 375°F(190°C). Grease a 2-quart baking dish with cooking spray; set aside.
Whisk together mayonnaise, sour cream, mustard, miso (if using), lemon zest, and garlic in a large bowl. Stir in cream cheese until fully combined. Fold in spinach, artichokes, 2 ½ cups of the Monterey Jack cheese and 1 ¾ cups of the Parmigiano until evenly distributed.
Transfer to the prepared baking dish and sprinkle evenly with the remaining ½ cup Monterey Jack and remaining ¼ cup Parmigiano.
Bake until the edges are bubbly and the cheese on top is light golden brown, 25 to 30 minutes. Let sit to cool slightly for 5 minutes. Serve hot with crackers, pita chips, tortilla chips, and/or crudités.
