There is a huge abundance of fruit in September.  Still some peaches, plums, grapes and nectarines while apples and pears are pouring in.  What to bake?  Tough decision, I decided to go with something I rarely use: we love juicy ripe plums but I seldom bake with them.  This is one of the only recipes I can make gluten free with blue plums; these are those oval plums, sometimes called prune or Stanley plums that are only available for a few weeks in the early fall.  They are inexpensive, not too sweet and they get soft and purply delish in this simple tart.  It is modeled closely after German plum tarts I had enjoyed in my wheat loving past life.  I think it replicates them quite well.  I posted this last year (2014) but wanted to share it again. This time I found really huge Stanley plums and tried them…