Step 1

Cook pasta in a large pot of boiling salted water, stirring occasionally, until very al dente, about 3 minutes less than package directions.

Step 2

Meanwhile, cook garlic and 1/4 cup oil in a large heavy pot over medium heat, stirring occasionally, until garlic is golden, about 4 minutes. Add anchovies (if using) and red pepper flakes and cook, smashing anchovies with a wooden spoon to break them up, until anchovies begin to dissolve, about 1 minute.

Step 3

Add 1 1/4 cups pasta cooking liquid along with 1 cup Parmesan to pot with anchovies and garlic and cook, stirring, until cheese is melted, about 1 minute. Using tongs, add pasta to pot, then add butter and lots of black pepper. Cook, tossing energetically and adding more cooking liquid if needed, until pasta is al dente and sauce is thickened and coats pasta, about 4 minutes. Remove from heat; add parsley, lemon zest, and lemon juice.

Step 4

Divide pasta among bowls; drizzle with oil and top with more Parmesan.