Bring a large pot of salted water to a rolling boil. Add the spaghetti and cook until just al dente, about 8-10 minutes, stirring occasionally.
While the pasta cooks, crush the garlic cloves with the flat side of a knife, releasing a fragrant aroma. Tear the basil leaves into smaller pieces and set aside.
Heat 1.5 tablespoons of olive oil over medium heat in a deep skillet. When shimmering, add the crushed garlic and sauté until golden and fragrant, about 1-2 minutes. Be careful not to let it burn.
Add the chopped, slightly overripe tomatoes to the skillet. Cook gently, stirring occasionally, until the tomatoes break down and release their juices, about 10 minutes. The sauce should become glossy and thick.
Season the sauce with salt, pepper, and red pepper flakes if using. Taste and adjust the seasoning as needed.
Drain the cooked spaghetti, reserving about half a cup of pasta water. Add the pasta directly into the skillet with the tomato sauce.
Toss the pasta gently in the sauce over low heat, adding a splash of reserved pasta water if needed to loosen the sauce and help it cling to the noodles.
Remove from heat and fold in torn basil leaves. Drizzle with the remaining olive oil, and give everything a gentle toss to combine.
Transfer the pasta to serving plates, garnishing with extra basil if desired. Serve immediately while hot and fragrant.
