Ask most Italians for a family recipe for pasta al pomodoro and they'll struggle, not because it's forgotten, but because it was never really taught. It's absorbed, the way you absorb how to boil water.
Tomatoes arrived in Italy from the Americas in the 1500s but were treated with suspicion for nearly two centuries — thought to be poisonous, or fit only for decoration. It wasn't until the late 1700s/early 1800s, particularly around Naples, that tomatoes and pasta were paired together in earnest, and even then it started as street food — maccheroni eaten by hand, dipped in sauce, sold by vendors to hungry passersby.