Preheat oven to 425ºF.
In a medium-size mixing bowl, combine the spinach, ground turkey, grated onion, half of the garlic, 1 egg, breadcrumbs, Parmigiano, mozzarella, nutmeg, salt and pepper. Work the mixture together with your hands until combined and set aside.
Spread one of the pizza doughs out onto the counter. Cut in half widthwise and in thirds lengthwise, making 6 squares. Take a handful of the meat mixture (about 1/4 cup), shape into a meatball and drop it onto the corner of one of the squares. Continue in this way until there's a meatball on each square.