How to archive a file using cron?

Question

Task Schedulers

Command added to cron:

zip /var/www/sites/www/site.ru/upload/archive.zip /var/www/sites/www/site.ru/upload/file.txt

After executing such a command, it is not the file file.txt itself that gets to the root of the archive, but the full path to it. Those. in the archive, this file can be reached as follows:
/var/www/sites/www/site.ru/upload/file.txt
What command can add only the file itself to the root of the archive, without subfolders?