Accessing private services

I have webserver apache nginx and I used reverse proxy to my python web servers on port 8000
anybody now using my domain.com and using nginx users can use my python web service

in other side I have other webserver in other country nginx installed
i want to be able to use most secure way for these 2 servers to connect with each other

so people who access my second server can access my first server app which is run on port 8000

Please recommend me best practice
if how it’s possible to use Cloudflare zero-trust