Bring a large saucepan of water to a boil and season with salt. Add the spaghetti and cook until al dente, according to package directions.
Meanwhile, in a large skillet over medium-high heat, combine the anchovies and their oil, the extra virgin olive oil, and the garlic. Cook gently, prodding occasionally, until the anchovies have dissolved and the garlic is aromatic, but not burnt, about 3 minutes.
Squeeze in the lemon juice and add the chopped parsley and stir to incorporate. Remove from the heat until the pasta is cooked.
Once the pasta is done, use a pair of tongs to pull the pasta from the saucepan into the anchovy pan, allowing some of the salted cooking water to go in with it.
Set the skillet over low heat and pull the spaghetti up and down in the pan to absorb the flavors and to help emulsify the oils with the starch of the cooking liquid.
Season with freshly ground black pepper and a pinch of red pepper flakes and finish with a few grates of lemon zest. Serve with rustic bread on the side, if desired.
