01 - Bring a large pot of salted water to a rolling boil. Cook the penne or fettuccine until al dente according to package directions. Drain the pasta, reserving 1/2 cup of the starchy cooking water.
02 - Heat the olive oil in a large skillet over medium heat. Sauté the finely chopped onion for 3–4 minutes until translucent. Add the minced garlic and cook for 1 minute until fragrant, taking care not to brown it.
03 - Pour in the crushed tomatoes and stir in the sugar, salt, black pepper, and red pepper flakes. Let the mixture simmer for 8–10 minutes, stirring occasionally, until the sauce slightly reduces and thickens.
04 - Reduce the heat to low and stir in the heavy cream. Allow the sauce to simmer gently for another 2–3 minutes to meld the flavors and create a cohesive texture.
05 - Transfer the drained pasta into the skillet with the sauce. Toss vigorously to coat the noodles evenly. Gradually add splashes of the reserved pasta water if necessary to achieve a silky, creamy consistency.
06 - Remove the skillet from the heat. Fold in the torn fresh basil leaves and the grated Parmesan cheese. Taste the dish and adjust the seasoning with salt or pepper as needed.
07 - Plate the pasta immediately in warmed bowls. Garnish with additional grated Parmesan and fresh basil leaves if desired.