Help in identifying a C. S. Lewis story

My information may be totally wrong, but I was told a long, long time
ago in a galaxy far, far away that C. S. Lewis wrote a story with
roughly the following plot:

A space traveller is marooned on a primitive planet. The inhabitants,
not understanding his advanced technology, believe he is some sort of
deity. Using his technology, he heals people "with a touch", and
performs various other "miracles". He is persecuted by the government
and is eventually captured and put to death on the rack. Many years
(decades, centuries) later, other people from his race make official
contact with this planet, which is now more advanced. People on this
planet still worship the memory of the "deity" that visited them, and
many wear a symbol of two interlocking squares, which resemble the
rack on which the traveller was executed.

Does this ring any bells with anyone? Was this written by someone
else? Or did I dream up this story?

Thanks to any and all who can help.

Live