Can't change the world frame

[Pierritop]

Hi, I'm having trouble with my coding.
I want my base frame to rotate by 45° around the x axes so that a displacement along the z axes has a 45° angle.
I only found transformations to express in the body frame or the base frame but none on how to express everything in an external frame.
If you have any clue on which instruction in libfranka I should use, I would really appreciate.