Melt 1 tablespoon of butter with 1 tablespoon of olive oil in a sauté pan over medium heat. Add the finely grated garlic clove and breadcrumbs and cook, stirring constantly, for 2 to 4 minutes or until the crumbs are lightly browned. Transfer the crumbs to a bowl and toss with the lemon zest. Set aside. Wipe out the pan.

Put a large pot of about 3 quarts of water on to boil with 1 tablespoon of kosher salt. Add the spaghetti and cook to al dente following the package directions. Reserve 1 cup of the cooking water and drain the spaghetti.

Meanwhile, cut the butter into chunks and put it in a small food processor with the anchovy fillets; process until the mixture is smooth. Melt the butter and anchovy mixture in the same sauté pan over medium heat. Add the mashed garlic halves and crushed red pepper and continue cooking for 4 to 5 minutes or until the butter is lightly browned. Remove the pan from the heat.

Add the drained spaghetti to the pan and toss with the anchovy butter. Place it back on medium heat and continue tossing, adding some reserved cooking water a little at a time until the sauce looks creamy. Add extra butter if you like. Taste and season with lemon juice, salt, and freshly ground black pepper to taste.

Transfer the pasta to a serving dish and top with the crumbs and chopped fresh parsley.