- Add the tomatoes to a deep, large bowl. Using your hands, crush the tomatoes until no large pieces remain, just a coarse tomato puree.
- Peel the garlic cloves and finely chop.
- Heat the olive oil and butter in a large pot over medium heat. Add the onion and garlic and season with salt and pepper. Cook, stirring occasionally until the onion is softened but not browned, about 10 minutes.
- Add the anchovies and the oil they are packed in. Cook, stirring occasionally until dissolved into the oil, about 2 minutes.
- Add the red pepper flakes and stir to combine.
- Add the tomato paste and cook until it turns a dark, brick-red color, about 4 minutes (this caramelizes the sugars in the tomato, which will give a really great flavor and take the edge off that raw tomato-y taste).
- Add the wine and cook for about 1 minute, just to burn off the alcohol.
- Add the tomatoes and stir everything together, making sure to scrape the bottom of the pot to get all those good bits. Add water and bring it to a boil.
- Reduce the heat to medium-low and cook the sauce for 1½–2 hours at a very low simmer; there should just be a few bubbles here and there. If medium-low is too high (every stove is different), reduce the heat to low. Stir every 30 minutes.
- Ladle out about 2 cups of sauce: This is what is known as your “extra sauce.” You’ll serve it alongside the pasta or freeze it for later.
- To serve, cook the spaghetti in a large pot of salted boiling water.
- Drain the pasta and add it to the sauce. Serve it right out of the pot, or transfer to a serving bowl. Top with grated Parmesan cheese.