Preheat oven to 375°F.
Heat the oil in a large sauté pan over medium heat. Once the oil is hot, add the roasted red peppers and shallot, and cook, stirring often, until the shallot is translucent, 2 to 3 minutes.
Add the garlic and season with the salt, chili flakes, pepper, and lemon zest. Continue to cook while stirring, until the garlic is fragrant, 2 to 3 more minutes.
Working in batches, add the spinach into the sauté pan. Continue to cook while mixing, until the spinach is wilted. Keep adding portions of spinach in batches until all the spinach has been added into the pan and cooked down. Most of the moisture should have cooked out of the spinach as well.
Reduce the heat to low and pour in the cream cheese and mayonnaise, stirring to combine. Sprinkle in the mozzarella and ½ cup parmesan and stir until most of the residual heat melts the cheeses. Last, mix in the artichoke hearts and lemon juice, and mix once more to combine.
Transfer the dip to a prepared 8x11-inch baking dish and top with the remaining ½ cup parmesan cheese. Cover tightly with foil and bake in the preheated oven until the cheese on top has melted, 25-30 minutes. Remove the foil and bake until bubbly and golden-brown, another 10 to 15 minutes.
Serve with chips, toasted bread, and veggies. Enjoy!