Cook pasta according to package directions until al dente, reserving 1 cup of the cooking water; drain pasta.

Make the sauce in the same pot: add ricotta, parmesan, lemon zest and juice, salt and pepper to taste and stir well.

Stir in 1/2 cup pasta water until smooth.

Add pasta and stir vigorously until pasta is well coated. Continue adding pasta water as needed, until smooth.

Stir in the arugula and serve immediately topped with remaining sauce from pan, extra parmesan, red-pepper flakes, and torn basil.