For the Dough

• In the bowl of a stand mixer fitted with the dough hook, add 4 ¾ cups of the flour, yeast, sugar, and salt. With the motor on low speed, add the oil and water; knead until a rough ball forms, about 45 seconds. Cover the bowl with a towel and let the dough rest for 2 minutes. Knead the dough on medium speed for 2 minutes. (If the dough appears to be very wet, add the remaining ¼ cup flour 1 tablespoon at a time as needed.)
• Turn the dough out onto a lightly floured work surface and form it into a smooth round ball. Place the dough in a large, lightly oiled mixing bowl and cover with a sheet of plastic wrap. Let rise in a warm, draft-free place until doubled in size, about 1 to 1 ½ hours.
• Adjust the oven rack to lower-middle position and preheat to 425ºF. Line the rimmed baking sheet with a sheet of parchment paper. Lightly oil the paper with more olive oil, about 2 tablespoons. Turn the dough out onto a lightly floured work surface and flatten it into a rough rectangle. Roll the dough into a 16 x 12-inch rectangle and press into the prepared pan. Shape the dough along the edges of the pan and brush it lightly with olive oil. Cover with plastic wrap and let rise until puffy, about 30-45 minutes.
• Dimple the dough with your fingertips, then sprinkle ¼ cup of the Parmesan cheese evenly over the dough. Bake until the parmesan begins to brown, about 8-10 minutes. Working quickly, spread the pizza sauce over the dough, leaving a ¾-inch border around the edge. Sprinkle the sausage, pepperoni, and onion evenly over the sauce. Bake until the sauce darkens and dries out, about 8-10 minutes. Working quickly, sprinkle the remaining parmesan and mozzarella over the dough. Continue to bake until the cheese is melted and lightly browned, about 10-15 minutes, rotating the pizza halfway through baking.
• Let the pizza cool in the pan for 1 minute. Using a large, wide spatula, lift the pizza, without the parchment, onto a large wire rack and allow to cool for at least 5 minutes. Transfer the pizza to a cutting board and cut into 16 squares. Serve hot or warm with crushed red pepper flakes. Enjoy!