Place the cauliflower florets in a food processor and pulse until the cauliflower is the size of rice.
Transfer the riced cauliflower to a large microwave-safe dish and cook uncovered at 100% for 8 minutes. Allow it to cool, stirring occasionally.
Meanwhile, heat 1 tablespoon of olive oil in a medium skillet over medium-low heat. Once hot, add the onion and sauté for about 10 minutes until the onion is soft and slightly browned.
Add the garlic and spinach. Cook, stirring, until the spinach wilts, then remove from heat and set aside.
Place the cooled cauliflower rice in a large, clean dish towel. Over the sink or a large bowl, twist and squeeze to remove as much liquid as possible, then transfer the cauliflower rice to a dry mixing bowl.
Add the egg, shredded mozzarella, pepper, and oregano. Mix well.
Preheat the oven to 450°F. Brush 1½ tablespoons of olive oil in a 10-inch ovenproof skillet, making sure the surface is completely covered.
Press the cauliflower mixture evenly into the skillet.
Place the skillet over medium heat on the stovetop and cook the crust for about 5 to 7 minutes or until it’s starting to brown around the edges.
Transfer the skillet to the oven and bake for 10 to 15 minutes. Once the crust is golden, remove from the oven and allow to cool for 5 minutes.
Spread the mozzarella slices, spinach mixture, and artichoke hearts over the crust, then sprinkle with Pecorino-Romano or Parmesan cheese.
Place back in the oven and bake until the cheese melts, about 5 minutes.
Sprinkle with fresh arugula.