01 - Preheat oven to 375°F. Grease a 9-inch springform pan with olive oil and line the base with parchment paper.
02 - Boil rigatoni in a large pot of salted water until very al dente, about 2 minutes less than package instructions. Drain and toss with 1 tablespoon olive oil. Set aside.
03 - Heat olive oil in a saucepan over medium heat. Sauté chopped onion until translucent, 3 to 4 minutes. Add minced garlic; cook for 1 minute. Stir in crushed tomatoes, tomato paste, oregano, basil, sugar, salt, and pepper. Simmer 15 to 20 minutes, stirring occasionally. Adjust seasoning to taste.
04 - In a mixing bowl, combine ricotta, 1 cup mozzarella, Parmesan, egg, chopped parsley, salt, and pepper. Stir until smooth.
05 - Stand cooked rigatoni upright, tightly packed, in the prepared pan. Using a piping bag or small spoon, fill each tube with the ricotta mixture.
06 - Pour the tomato sauce evenly over filled pasta, allowing it to seep between noodles. Sprinkle remaining mozzarella evenly over the top.
07 - Cover loosely with foil and bake for 30 minutes. Remove foil and continue baking for 15 minutes, until cheese is golden and bubbling.
08 - Allow to rest for 10 minutes before releasing the springform pan. Garnish with extra parsley and Parmesan. Slice and serve warm.