How to save a TextureRenderTargetCube to a file

Hi,I want to save a TextureRenderTargetCube in disk as a png file 。But i can not get FTextureRenderTargetCubeResource,there has not a function to get it。when i use GameThread_GetRenderTargetResource() i can get a FTextureRenderTargetResource 。
but this can only save one face of a cubemap,even i use this sentence to set the cubeface ,
FReadSurfaceDataFlags ReadPixelFlags(RCM_UNorm, ECubeFace::CubeFace_NegY);
it still can not change the face

my question is same to you, expect the next answer.

my question is same to you, expect the next answer.