Over some kugel last night, I asked my son how he would spell "lukshen" as in "lukshen kugel". He though for only a moment before rattling off: l-u-c-t-i-o-n. I love him. He is for sure his mother's son. When I told him that Rivka said that it ought to be spelled "lukshen", he said that you were probably right, the "Latin t-i-o-n is unlikely in this case."
Still, I know for sure that I've seen "luction" in cookbooks, including a quite old one. Which, if I had a scanner thing, I'd scan and show you. But I don't, so y'all will just have to trust me.