Fill a large pot with water for the pasta and bring it to a boil.
While you wait for it to boil, assemble the ingredients for the sauce: olive oil, garlic, chili pepper, walnuts, anchovies (or paste) and lemon juice. The sauce will come together quickly, so assembling the ingredients now will save time.
When the water boils, generously salt and add the pasta.
Cook pasta according to package directions, minus 3 minutes for perfect al dente pasta.
The sauce will only take about 5 minutes, so start the sauce when there are 5 minutes left on the pasta cooking time.
In a large sauté pan, heat the olive oil over medium heat.
Add the garlic, chili flakes and walnuts and toast for about 3-5 minutes. Adjust the heat and lower it to prevent the garlic from browning. You want it to gently simmer, so adjust heat accordingly.
Add the anchovies (or paste).
If using anchovies, press them down into the sauce with the back of a wooden spoon. They will melt into the sauce, so keep pressing until they are fully incorporated. This should only take a minute or two. If you finish this step and your pasta is still cooking, remove your skillet from the heat and set aside. When you're ready to add the pasta water and then the pasta, place it back on low to medium heat to warm it.
When the pasta is finished cooking BEFORE DRAINING, scoop out 1 cup of pasta water into a glass measuring cup. The pasta water will help bring the sauce together and coat your pasta. Drain the pasta and return to the pot, drizzle with olive oil and add a couple tablespoons of butter (this will prevent the pasta from sticking together).
ANOTHER OPTION FOR THE PASTA: You can also use tongs to transfer pasta straight from the pot directly to the sauté pan. There should be enough water on the pasta to help the sauce, but save some of the pasta water in case you need to add a bit more. If you do it this way, be sure to turn off the heat on your stove first.
Carefully stir the pasta water into the sauce. The starch in the water will help the sauce coat the pasta and create a beautiful glossy sauce.
Using tongs, add the pasta to the saucepan , and toss with the sauce until it's fully coated with the sauce. The pasta should look gorgeous and glossy.
Add the lemon juice, and toss a few more times over low heat.
Serve garnished with some parsley, and with a sprinkling of Parmesan cheese.
You can also drizzle a little bit of olive oil over the top because, well, why not?
