S flower and sadistic beauty are both really good, even if the femdom isn't really 'caring'. The femdom in Sadistic beauty is probably a tad bit better than S flower's, but sadly sadistic beauty got dropped. Besides those two the only other dominatrix webtoon I've ever seen is No Holes Barred... but the femdom is by far the absolute worst protagonist out of all of them. The first time she and her sub get it going it's pretty much rape :/ sorry it's not much, but it's all I've got.
http://www.mangago.zone/read-manga/sadistic_beauty/
http://www.mangago.zone/read-manga/s_flowers/
http://www.mangago.zone/read-manga/no_holes_barred/
Some femdom manga or webtoon with good storyline, where the woman isn't overly sadistic and abusive, but dominant and caring. (▰˘◡˘▰)