Heat 2 tablespoon of the olive oil in a saute pan. Add the red onion, 1/4 teaspoon salt, and a few pinches of pepper; saute over medium heat for 4 to 5 minutes, until tender. Add half of the garlic and saute for i minute. Transfer to a bowl.
Heat 2 tablespoon of olive oil in the pan. Wilt the spinach over high heat with 1/4 teaspoon salt, a few pinches of pepper, and the remaining garlic. When the spinach is wilted but still bright green, in about i minute, remove it from the pan and place it in a strainer to cool. Squeeze out the excess moisture with your hands, then coarsely chop and toss with the lemon zest.
Preheat oven to 500°F.
Roll out the dough and place it on a lightly oiled pizza pan or well-floured wooden peel; brush with the Garlic Oil. Spread the onion on the dough, followed by the spinach. Sprinkle the olives over the spinach, follow with the crumbled feta, then add the mozzarella cheese.
Bake the pizza, in the pan or on a preheated pizza stone, for 8 to 12 minutes, until the crust is golden and crisp.
Remove it from the oven and sprinkle with the Parmesan cheese and fresh rosemary.