There are some methods to check the ownership of a domain name in the cPanel/WHM server. Below are the command lines and for each one described, you may copy and execute any of them as your own wish:
locate $domain
Before executing the above command, make sure, locate is already installed on the server. If not, execute the following command line to install and update the meta DB:
yum install mlocate -y --skip-broken && updatedb
Check through the official script of cPanel:
/scripts/whoowns $domain
Check through the user's database of cPanel:
grep $domain /etc/userdomains
Do not forget to replace your domain name instead of $domain