Huernia bayeri

Don't think spelling makes any difference? The genus was named for Justus van Heurne (1577-1652) but his name was misspelled by Robert Brown and, in accordance with botanical naming rules, Mr Heurne is forever remembered by a misspelling of his name. This particular species has more than it's share of names given to it also, but we'll stick with this name for now. (The centers of the flowers are sometimes purple and sometimes mostly yellow.)
This is one of the more readily available of the huernias and is in many collections. The ease of its cultivation and the prolific flowering may well account for it.