Apex domains cannot have CNAME records.
Question and response
Question
dig convergia.net. NS
Answer
convergia.net. 5 NS ns3.convergia.net.
convergia.net. 5 NS ns1.convergia.net.
convergia.net. 5 NS ns2.convergia.net.
Authority
The response has no authority records.
Additional
ns1.convergia.net. 5 A 204.10.207.34
ns2.convergia.net. 5 A 204.10.207.39
ns3.convergia.net. 5 A 204.10.203.184
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0