Spinach-Feta Pizza

Preheat the grill for direct cooking over medium-high heat. If using charcoal, spread 2/3 of the hot coals on one side; spread the remaining 1/3 on the other side. If using a gas grill, reduce the heat on 1 side to medium.Heat 3 teaspoons olive oil in a large nonstick skillet over medium-high heat. Saute garlic until fragrant, about 30 seconds. Add the spinach and simmer until the spinach wilts, 1-2 minutes. Transfer to a small bowl.For 14-inch-wide pizza cakes, sprinkle with flour or cornmeal; flour the work surface. Roll out the dough into a 12-inch circle. Spread the dough on the pizza crust; brush with the remaining 2 tsp butter.The fillings should be within reach of the grill. Place the dough on the hot part of the grill; cover the grill. Cook, rotating, until the bottom is bubbling and browned, about 2 minutes. Place the dough on the colder side of the grill, cooked side up. Spread the pizza crust with the sauce; top with the mozzarella, leaving a 1/2-inch thick rim. Top with the spinach mixture and sprinkle with feta.Cover the grill and cook until the bottom crust is browned and the cheese is melted, 2 to 3 minutes, occasionally removing the lid and checking the bottom of the crust to make sure it doesn't burn. If it is cooking, reduce the heat (if using a gas grill) or remove the grill (if using charcoal). Transfer the pizza to a cutting board. Let stand for 2 minutes, then slice and serve.