01 - Bring a large pot of salted water to a boil. Cook the pasta according to package instructions until al dente. Reserve 1/2 cup of pasta water, then drain the pasta.
02 - While the pasta cooks, heat olive oil in a large skillet over medium heat. Add onion and sauté for 3-4 minutes until translucent. Add garlic and cook for another 30 seconds.
03 - Pour in the crushed tomatoes, sugar, salt, black pepper, and red pepper flakes (if using). Simmer for 8-10 minutes, stirring occasionally.
04 - Reduce heat to low. Stir in the heavy cream and cook for 2 minutes, until the sauce is creamy and well combined.
05 - Add the cooked pasta and reserved pasta water to the sauce. Toss to coat evenly.
06 - Stir in grated Parmesan and fresh torn basil. Adjust seasoning if needed.
07 - Serve immediately, garnished with extra Parmesan and basil leaves.