How can I rotate an actor around his up vector ?

Hello, In my 2D project I have an actor that walks on hills and such which causes his up vector to not always be Z=1

How would I rotate him 180 around HIS up vector (Basically using his up vector as an axis of symmetry) ? Simply entering “180” in the yaw cannot work since when he is on a hill his up vector’s coordinates are something like X =, Z =