How to Make It
Heat oven to 400° F with a rack in the lowest position. Heat 1 tablespoon of the oil in a medium skillet over medium-high heat. Add the sausage and cook, breaking it up into large pieces with a spoon until golden brown but still pink in the middle, 4 to 6 minutes.
Coat a 9-inch cake pan with 1 tablespoon of the oil. Press the dough into the pan, covering the bottom and sides. Top the dough, in this order, with the mozzarella, marinara, onion, and cooked sausage. Bake until the crust is golden brown, 30 to 35 minutes. Top with the ricotta and ¼ teaspoon pepper. Bake until the ricotta is warm, 3 to 4 minutes more. Let rest for 5 minutes before serving.
Meanwhile, toss together the romaine, lemon juice, the remaining 2 tablespoons of oil, and ¼ teaspoon each salt and pepper in a medium bowl.
Serve the pizza warm topped with half of the romaine. Serve the remaining romaine on the side.