Some images I’ve just received from Dick Houtenbos (thank you!), who grows peonies in Morocco where this species grows in open places in the forest. As far as I know, Paeonia coriacea is the only species growing wild in Morocco, thus there can be little doubt that this would be the species (and it fits with other images I’ve seen of this species). When in bud and just open it’s somewhat darker, fading paler very soon.