Apex domains cannot have CNAME records.
Question and response
Question
dig dc.volia.com. NS
Answer
dc.volia.com. 5 NS ns5.dc.volia.com.
dc.volia.com. 5 NS ns0.dc.volia.com.
dc.volia.com. 5 NS ns1.dc.volia.com.
Authority
The response has no authority records.
Additional
ns0.dc.volia.com. 5 A 82.144.220.7
ns5.dc.volia.com. 5 A 77.120.112.133
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0