Looking for a fantasy with a female mastermind.

I'd love to read a medieval fantasy where a female character is a secret genius mastermind pulling the strings of a kingdom or organization using her husband or brother or other male confidant as a figurehead.

A classic medieval setting with people that have specific views about women and gender roles which makes it that much easier for our protagonist to weave her web and that much more jarring when her enemies find out who really has the power.