In a large pot, bring 4 quarts water and 1 tablespoon salt to boil. Add spaghetti and cook until al dente, about 9 to 10 minutes. Reserve 1 cup pasta water and drain well.: When the water reaches a rolling boil you will notice a lively sound and rapid movement at the surface, which means the spaghetti will cook evenly. Salted water seasons the pasta from the inside out, so do not skip it. A common mistake is under salting the water, which leads to bland pasta even when the sauce is strong, so taste a strand early to check seasoning.
In a large Dutch oven or saucepan, heat oil over medium heat until shimmering. Add garlic and cook until garlic begins to turn golden, but not scorched, about 1 minute.: You will hear a softer bubbling as the pasta hydrates and see the noodles become plump and slightly translucent. Test by biting for a tender center with a subtle chew, that is al dente. Overcooking will lead to mushy texture and a sauce that slides off rather than clings, so start checking at around 7 minutes if your brand cooks quickly.
Stir in capers, anchovy fillets, olives, tomatoes, and crushed red pepper (I like 1 teaspoon). Heat to boiling, reduce heat, and simmer uncovered until slightly thickened, about 30-40 minutes.: The reserved starchy pasta water will look slightly cloudy and feels slick between your fingers, and it s invaluable for thinning and emulsifying the sauce. Drain the pasta thoroughly to avoid pooling water that can dilute the sauce, but keep that cup close at hand.
Add the pasta to the pot with the sauce and toss until evenly coated. Thin with pasta water if needed. Serve with Parmesan cheese and garnish with fresh basil.: You will see a gentle ripple across the surface of the olive oil and smell its fruitier notes when it s ready. This is the moment to add aromatics, because the oil will carry their flavors. Avoid heating until smoking, which can make the oil bitter and ruin the dish.
Add garlic and cook until garlic begins to turn golden but not scorched about 1 minute: As the garlic sizzles you will detect a fragrant, toasty aroma that signals flavor release. Aim for a warm, light golden hue; anything darker tastes acrid. Stir constantly to ensure even coloring, and remove from direct heat if it starts to brown too quickly.
Stir in capers anchovy fillets olives tomatoes and crushed red pepper I like 1 teaspoon: Once these ingredients hit the warm oil, they will release a layered fragrance of brine and umami while the canned tomatoes begin to break down. Mash the anchovy fillets against the pan so they dissolve and meld into the oil, which prevents isolated fishy bites and builds a cohesive base. A common pitfall is adding everything too quickly and not allowing flavors to integrate, so stir and let them mingle before reducing heat.
Heat to boiling reduce heat and simmer uncovered until slightly thickened about 30 to 40 minutes: During the simmer you will notice the sauce reduce, becoming deeper in color and more concentrated in aroma, with gentle popping as moisture escapes. This slow concentration is why the sauce develops its bold character, so be patient and keep the pan uncovered to allow evaporation. Avoid high heat which can break the sauce into an oily separation rather than a cohesive coating.
Add the pasta to the pot with the sauce and toss until evenly coated: When you combine the spaghetti with the sauce, you should hear a light sizzle and see the noodles glisten as they pick up the tomato and oil emulsion. Tossing rather than stirring ensures the sauce wraps around each strand. If the sauce seems too thick, add small splashes of the reserved pasta water to loosen and create a silky finish; too much water will make it soupy, so add gradually.
Thin with pasta water if needed: The right amount of starchy water will create a glossy, clingy texture that holds onto the spaghetti . Add no more than a few tablespoons at a time until you reach the desired sheen and consistency. A mistake here is over thinning, which dilutes flavor, so judge carefully by how the sauce coats the pasta.
Serve with Parmesan cheese and garnish with fresh basil: As you plate, grate fresh Parmesan cheese over the top to introduce a nutty finish and scatter torn basil leaves for aroma. The contrast between warm pasta and fresh herb is immediate and uplifting. Serve promptly for the best texture, because sitting too long will soften the basil and the pasta will keep absorbing sauce.