Why not use the free Canon DPP 4.5.1 software that came with your EOS 6D? Here is my attempt with that software:
With the recipe file (just change the .txt extension to .dr4 before you use it): moon.txt (7.4 KB)
In case you really want to try out Rawtherapee, here is the same image processed with RT:
IMG_3420-1.jpg.out.pp3 (9.9 KB)
