Mr. Guetta, now 64, then set the table with the new wheat. He sautéed the Swiss chard, incorporating it into a frittata, and he turned the red pumpkin into one of several jams, this one slightly savory with garlic and cumin. He used no salt in the meal that followed, in deference to the holiday’s traditional wish for sweetness in the year to come.

And, because almost every Libyan Jew starts the Rosh Hashana meal with a spicy fish dish called aharaimi, he made that, too.

“When the professor saw what I had done,” Mr. Guetta said, “he was surprised and became very emotional.”

In the third century B.C. , the first Jews arrived in what was then the Greek colony of Cyrene , and is now part of Libya. It was never a large Jewish community, said Mr. Guetta, but it stuck together. Michael Berenbaum, a professor of Jewish Studies at American Jewish University in Los Angeles and one of the editors of the Encyclopedia Judaica , said that in the 1940s there were about 44 synagogues in Tripoli alone; practically no Jews live in Libya today.

According to Dr. Berenbaum, more than 30,000 Jews left Libya between 1949 and 1951. Most went to Israel, and the rest went to Italy. ( They were already proficient in the language, following Italy’s occupation of Libya in the first half of the 20th century. ) After the Six-Day War in 1967, another 6,000 Libyan Jews went to Italy, with others gradually moving during the intervening years.