calibredb listing authors that begin with a certain letter

I am trying to search through my books and print out only books whose author begins with a certain letter.

So for example if I run something like:
calibredb list --fields authors --search authors:A

It would return a list of authors whose names start with the letter 'A'.
I tried the above method, but that returns authors whose name HAS an 'A'

I also tried:
calibredb list --fields authors --search authors:=A
But this returns authors whose names are 'A', which in my database are none so that is no help.

Any ideas??