Apex domains cannot have CNAME records.
Question and response
Question
dig regusnet.com. NS
Answer
regusnet.com. 4 NS udns1.cscdns.net.
regusnet.com. 4 NS udns2.cscdns.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0