01 - Bring a large pot of salted water to a rolling boil. Cook penne pasta according to package directions until al dente, then reserve 1/2 cup of the starchy cooking water before draining thoroughly.
02 - Heat olive oil in a large skillet over medium heat. Sauté garlic and diced onion for 2-3 minutes until fragrant and translucent, being careful not to burn the garlic.
03 - Add diced tomatoes, tomato paste, oregano, chili flakes, salt, and pepper to the skillet. Simmer for 5-7 minutes, stirring occasionally, until the sauce slightly thickens and flavors meld together.
04 - Transfer the drained pasta directly into the skillet with the tomato sauce. Toss vigorously to coat each piece evenly, adding splashes of the reserved pasta water as needed to achieve a silky, emulsified consistency.
05 - Stir in the chopped fresh basil and grated Parmesan cheese. Cook for 1 minute just until the cheese melts and everything is thoroughly incorporated.
06 - Serve immediately while hot, topping each portion with additional fresh basil leaves and extra Parmesan cheese for presentation.