Zantedeschia elliotiana—yellow calla lily.  Information of Plantzafrica website leads me to believe that this is species Z. elliotiana, although I have been know to be wrong about these things.  Photographed in a private garden in Berkeley, CA
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/12303842@N00">John Rusk</a> from Berkeley, CA, United States of America
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/john_d_rusk/26704755340/">J20160510-0023—Zantedeschia elliotiana—RPBG</a>