Unfortunately I couldn't take a printscreen (it CTD-ed after Alt-Tab, that's why the debugg will be the same as in my CTD report).
My first city was next to fertile land. Fine! I built a workshop then a farm.
My second city was near 2 fertile tiles. Soon they were encompassed into my zone of influence but...farm icon didn't appear in the build window, even after the ZOI enlarged a little more.