I really liked MARD-019 for two reasons. One, it features Tsuyako Kano, who I find really sexy. Two, it's nice twist--Mom gives her son a beating for being fresh and then facesits and fucks him.
I've written about this title in other places here already, but it also fits here: it's not just fem-dom but mom-dom, yes. What also comes to mind is this one with Shihori since in it, she is dominant in general, "teaching" the son (OKSN-261). Also, other than my usual advice to search for key words (e.g. for the usual 母 and 息子, "mother" and "son" but also ドM, "masochistic"); this one seems to work as expected, judging by the thumbnails here; there are also some results on Fanza via Google for the combination of "mother" and "SM" but I cannot view them
