01 - Bring a large pot of salted water to a boil. Add penne pasta and cook according to package directions until al dente. Reserve 1/2 cup pasta water before draining.
02 - While pasta cooks, heat olive oil in a large skillet over medium heat. Sauté garlic and onion for 2-3 minutes until fragrant and softened.
03 - Add diced tomatoes, tomato paste, oregano, chili flakes, salt, and pepper. Simmer for 5-7 minutes, stirring occasionally, until sauce thickens slightly.
04 - Transfer drained pasta to the skillet with sauce. Toss thoroughly, adding reserved pasta water as needed to achieve silky consistency.
05 - Stir in chopped basil and Parmesan cheese. Cook for 1 minute until cheese melts and pasta is evenly coated. Serve immediately with additional basil and Parmesan.