All of the guests were Ashkenazim descended from European Jewry and keep to the custom of not eating kitniyot legumes on Passover. Davka, the most learned of the guests and his wife contributed a quinoa dish.
Quinoa is relatively new to many people.
Quinoa, a species of goosefoot, is a grain-like crop grown primarily for its edible seeds. It is a pseudocereal rather than a true cereal, or grain, as it is not a member of the true grass family. Wikipedia
There is a lot of controversy among Ashkenazi rabbis about whether it should be added to the list of forbidden legumes or not. This salad my neighbor brought looks like a bulgur salad, which is totally forbidden on Passover for all Jews. Instead it was a quinoa salad. Try this quinoa salad recipe leaving out the cheese.
It's ironic that it was davka these neighbors who brought the quinoa salad. They are very meticulous in their Torah observance. If it had been almost anyone else, almost nobody would have touched the quinoa. Here's the Machon Shilo explanation of quinoa and Passover.
2. Exactly 29 years ago I heard the very same opinion expressed by HaGaon HaRav Shaul Yisraeli z’l. The conversation took place right after Shaharith in Y’shivath Merkaz HaRav, a few days before Pesah. I asked him what his view was regarding qittniyoth. He responded that only those items that Ashk’nazim originally refrained from eating were forbidden. Therefore, he continued, soya beans are permissible because they were unknown in Europe at the time. He added that peanuts are mutar, and that in his home town in Russia, Slutzk, peanuts were the item of choice placed before guests during Pesah. He explicitly mentioned that this was done by all Jews in his town, including the Rav of the town, the world-renowned Gaon, HaRav Isser Zalman Meltzer, author of Even HaEzel on the Rambam, who later moved to Jerusalem.It makes sense to me. One thing is that I'm not looking for a food that has to be carefully checked. It's just more work when I don't have the time.
3. By the same logic quinoa may be consumed during Pesah even by those who refrain from qittniyoth; quinoa was unknown in the West till relatively recently.