Steve Martin -- My Pasta Tweet Got Racial ... SCUSA!

Steve Martin learned an important lesson about lasagna last night ... the dish can get racial.

The SNL alum was cracking grammar jokes on Twitter .. when someone asked, "is this how you spell lasonia?"

Steve's response ... "It depends. Are you in an African-American neighborhood or at an Italian restaurant."

Seconds later the 68-year old actor deleted the tweet and apologized. But the floodgates opened, the original tweet went viral and Martin atoned again: "I did apologize. But again, a second later I realized what an offensive thing I'd done ... In retrospect, bad joke."

A penne for his thoughts.