Bring a pot of well salted water to a boil. Add the pasta when the tomato sauce comes to a simmer. Reserve a mug of pasta water before draining.
Blend the canned tomatoes and tomato paste until smooth. Pour ½ cup of water into the empty tomato can, swirl to loosen any remaining tomato and add that to the mixture.
In a large skillet, add the olive oil and sliced garlic while still cold. Place over low heat and allow it to slowly come up to a very gentle sizzle, about 4–5 minutes.
Add the anchovies (and red pepper flakes if using) and cook for 1–2 minutes, stirring until mostly dissolved.
Add the capers and olives and gently sizzle for another minute.
Pour in the tomato mixture, stir well and bring to a gentle simmer. Cook for 10–15 minutes while your pasta cooks.
Add ¼ cup of pasta water into the sauce along with the cooked pasta.
Toss well and let it gently bubble for 1 - 2 mins until the sauce is clinging to the pasta.
Stir through the parsley and serve immediately with freshly grated parmesan.