Bring a large pot of salted water to a boil. Add the pasta and cook until al dente, according to package instructions. Reserve 1 cup of the cooking water, then drain the pasta.
In the same pot, make the sauce: Add the ricotta, Parmesan, lemon zest and juice and ½ teaspoon each salt and black pepper and stir until well combined.
Add ½ cup of the cooking water to the sauce and stir until smooth. Add the pasta and continue to stir vigorously until the noodles are well coated. Add more cooking water as needed for a smooth sauce.
Divide the pasta among bowls and top each serving with some of the sauce that has pooled at the bottom of the pot. Garnish with Parmesan, black pepper, red pepper flakes and basil (if using) and serve immediately.
