The right way is to define a separated server for the naked domain and redirect it.
<sxh bash>
server {
    listen 80;
    server_name example.org;
    return 301 $scheme://www.example.org$request_uri;
}

server {
    listen 80;
    server_name www.example.org;
    ...
}
</sxh>
**Note** that this also works with HTTPS site.