Bring 4 liters of water to a rolling boil in a large pot. Add 2 tablespoons of salt. Add 400 g penne and cook uncovered, stirring occasionally, until al dente (check package for time, typically 10–12 minutes). Reserve 1 cup (240 ml) of pasta cooking water, then drain the pasta.

Sauce Base

While the pasta cooks, heat 3 tablespoons olive oil and 1 tablespoon butter in a large sauté pan over medium heat. Add the finely chopped onion and cook, stirring occasionally, until soft and translucent, about 6–8 minutes. Add minced garlic and 1 teaspoon crushed red pepper flakes and cook 30–45 seconds until fragrant (do not brown).

Tomato Sauce

Stir in the 2 tablespoons tomato paste and cook 1–2 minutes to caramelize slightly. Add 800 g crushed tomatoes, 1 teaspoon dried oregano, 1 teaspoon dried basil, 1 teaspoon sugar (optional), 1 teaspoon salt, and 1 teaspoon freshly ground black pepper. Pour in 120 ml stock (or use some reserved pasta water) and bring sauce to a gentle simmer. Reduce heat to low and simmer, uncovered, 10–15 minutes to thicken and develop flavor, stirring occasionally. Taste and adjust seasoning.

Finish & Garnish

Combine and finish

Add the drained penne directly to the sauce. Toss to combine over medium heat for 1–2 minutes, adding reserved pasta water a few tablespoons at a time if needed to loosen the sauce and help it cling to the pasta. Stir in 1 tablespoon butter (optional) for a glossy finish and 1 cup grated Parmesan, reserving a little for serving. Fold in torn fresh basil. Drizzle with 1 teaspoon olive oil, taste and adjust salt and pepper.

Serve immediately, topped with additional grated Parmesan and extra basil if desired.