01 - Bring a large pot of salted water to a rolling boil. Add pasta and cook until al dente according to package directions. Reserve 1/2 cup of pasta cooking water before draining.
02 - Heat olive oil in a large skillet over medium heat. Add chopped onion and cook for 3-4 minutes until softened and translucent. Add minced garlic and sauté for 1 minute until fragrant.
03 - Pour crushed tomatoes into the skillet. Add salt, pepper, and sugar if using to balance acidity. Simmer for 10 minutes over medium heat, stirring occasionally.
04 - Reduce heat to low. Stir in heavy cream and grated Parmesan cheese. Simmer for 2-3 minutes, stirring continuously until sauce is creamy, smooth, and slightly thickened.
05 - Add drained pasta directly to the sauce, tossing vigorously to coat each piece thoroughly. Add reserved pasta water as needed to achieve desired sauce consistency.
06 - Remove skillet from heat. Gently fold in fresh basil leaves just until combined, preserving their vibrant color and aroma.
07 - Plate immediately while hot. Top with additional grated Parmesan cheese and fresh basil leaves as garnish.