Bring a large pot of generously salted water to a rolling boil. Add the spaghetti and cook until just shy of al dente, about 8-10 minutes, stirring occasionally. Drain the pasta, reserving a cup of pasta water, and set aside.
While the pasta cooks, heat the olive oil in a deep skillet over medium heat. Once shimmering and fragrant, add the thinly sliced garlic. Sauté for about 30 seconds until it turns golden and releases a nutty aroma—be careful not to burn it.
Add the torn basil leaves to the garlic and oil, stirring quickly for about 10 seconds. This releases their fragrant oils and infuses the oil with herbal aroma.
Pour in the chopped tomatoes, along with a pinch of salt, and stir to combine. Reduce the heat slightly and let the mixture simmer gently for 10 minutes, stirring occasionally. The sauce should thicken slightly and become vibrant and fragrant.
Taste the sauce and adjust seasoning with more salt if needed. If the sauce seems too thick, stir in a splash of reserved pasta water to loosen it and help it cling to the pasta.
Add the drained spaghetti directly into the skillet with the sauce. Toss with tongs or a fork to coat each strand evenly, allowing the sauce to cling and the flavors to meld. Cook for another minute so the pasta absorbs some of the sauce.
Finish by tearing the remaining basil leaves over the pasta, adding a final drizzle of olive oil, and cracking fresh black pepper on top. Toss gently to distribute everything evenly.
Serve immediately while the dish is warm, with extra basil and pepper if desired. The sauce should be glossy, with visible bits of tomato and fragrant basil, clinging to the pasta strands.
