Cook the spaghetti pasta in a large pot of salted boiling water according to package instructions until al dente.
Meanwhile, in a large skillet, heat the olive oil over medium heat.
Add the garlic and red pepper flakes to the skillet and cook until fragrant, about 1-2 minutes.
Add the anchovy fillets to the skillet and cook until they have dissolved into the oil, about 2-3 minutes.
Add the chopped Kalamata olives and capers to the skillet and cook for 1-2 minutes.
Add the diced tomatoes to the skillet and bring the sauce to a simmer.
Reduce the heat to low and let the sauce simmer for 10-15 minutes until it has thickened slightly.
Season the sauce with salt and pepper, to taste.
Drain the spaghetti pasta and add it to the skillet with the puttanesca sauce.
Toss everything together until the pasta is coated in the sauce.
Sprinkle chopped parsley over the pasta and serve hot.