Add the pasta to the boiling water and cook until al dente according to the package directions, stirring often. Place the peas in the sieve and cook them in the water until they’re warmed throughout, about 1 to 2 minutes if fresh, or 2 to 3 minutes if frozen. Set the peas aside.
Before draining the pasta, scoop out about ½ cup of the pasta cooking water with a heat-safe measuring cup. Drain the pasta, then return it to the pot. Pour in the green sauce, about ¾ of the Parmesan and the peas, and add a small splash of the reserved cooking water (not the end of the world if you forgot it). Stir gently until the pasta is well coated and bright green, adding another splash or two of pasta water to loosen the sauce and make it almost creamy.
Divide into bowls immediately. Top each with a sprinkle of the remaining Parmesan, a few dollops of ricotta, and a sprinkle of lemon zest and red pepper flakes (both optional). Finish the bowls with a light drizzle of olive oil. Enjoy! Leftovers will keep for up to 2 days in the refrigerator, covered (technically, they’ll last up to 4, but the flavor degrades as time goes on).
