Cook the Pasta: Fill a large pot with heavily salted water and bring it to a boil. Add the fettuccine and cook until it's just slightly underdone, shy of al dente. This ensures the pasta finishes cooking in the sauce later. Drain the pasta and set it aside.
Toast the Bread Crumbs: In a 10-inch skillet, heat the olive oil over medium heat. Add the panko bread crumbs and stir frequently, allowing them to toast until they turn a deep golden brown, about 5 to 7 minutes. Once toasted, transfer the bread crumbs to a separate bowl.
Make the Sauce: Using the same skillet, return it to medium heat and add the butter, chopped anchovies, and lemon zest. Stir the mixture as the butter melts, using a fork to mash and break up the anchovies until they fully integrate into the sauce.
Combine Pasta and Sauce: Add the drained pasta to the skillet with the anchovy mixture. Toss everything together and let the pasta cook briefly in the sauce, about 1 minute, until it’s fully coated and heated through. Remove the skillet from the heat, then stir in the lemon juice and the toasted bread crumbs. Toss the pasta to evenly distribute the flavors.
Garnish and Serve: For an optional finishing touch, sprinkle chopped fresh parsley over the pasta before serving. Enjoy immediately while warm.