This is the most critical, often rushed, step. Never drain your spaghetti completely. Reserve about a cup of the starchy, salty pasta water before you dump the rest. That liquid gold is the glue that binds your sauce and pasta together.
Transfer the hot spaghetti directly into the pan with your sauce. Toss vigorously with tongs for about 60 to 90 seconds over medium heat. Add splashes of pasta water until the sauce coats each strand luxuriously, not clumpy. This is called mantecatura in Italian.
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Finish with a drizzle of good extra-virgin olive oil and fresh grated Parmesan. That final minute of tossing is not optional—it’s where the magic happens. You’re emulsifying the sauce, making it silky.