EASA CPL(A) = written tests done.
Have you made a 50km glider flight? Or 100km with instructor?
Maybe the easiest way: Fly with an examiner. Submit the paperwork. Done.
What I did over several years: The British Gliding Association (BGA) issued me a glider license by mail after I provided copies of logbook pages and my FAA certificate. The German Luftfahrtbundesamt (LBA) gave me a PPL(C) after I flew with an examiner. After paperwork and money the PPL(C) became an EASA SPL.
The LBA permits flying D-registered gliders with most foreign certificates/licenses. Is that the case in Spain? Perhaps you can just fly with what you have. I did that for a whole soaring season in Germany.