You're rinsing the glue off the pasta

Yes — the most likely reason is you’re not using the starchy pasta water.

That cloudy, salty water is the glue that binds sauce to noodles. If you drain the pasta, rinse it, or dump all the water down the sink, you’re washing away the one thing that makes sauce cling. Same goes for under-salting the water: salt helps the starch release, and starch is what emulsifies with fat in the sauce.

The fix is dead simple: before you drain the pasta, scoop out a cup of the cooking water. Then, instead of dumping sauce on top of dry pasta, toss the hot pasta in the pan with the sauce over low heat, adding a splash of