What is the formula to calculate what rotation an object must have in order for this object to be perpendicular to a line from another object?

Question

Linear algebra

Given:
Object 1 is a character. We know its position and rotation in world coordinates.
Vector1 (x,y,z) - position of the character (object 1).
Rotator (x,y,z) - the current rotation of the character (object 1).
Object 2 is a screen.
Vector2(x,y,z) - screen position (a known point where the menu should be, calculated by getting the Forward Vector from the character + adding the required distance to it.).
Rotator2(x,y,z) - screen rotation (desired)
Picture for clarity. Image description:
Brown - earth.
Black is a character.
Blue is the distance to the screen.
Yellow is the screen.

What formula can be used to get the actual Rotator2 depending on the rotation of the character?