Apex domains cannot have CNAME records.
Question and response
Question
dig convio.net. NS
Answer
convio.net. 5 NS dns1.convio.net.
convio.net. 5 NS ns7.convio.net.
convio.net. 5 NS ns8.convio.net.
convio.net. 5 NS dns1.p01.nsone.net.
convio.net. 5 NS dns4.p01.nsone.net.
convio.net. 5 NS dns3.p01.nsone.net.
convio.net. 5 NS dns2.p01.nsone.net.
Authority
The response has no authority records.
Additional
ns7.convio.net. 5 A 74.123.153.5
ns8.convio.net. 5 A 74.123.154.138
dns1.p01.nsone.net. 2 A 198.51.44.1
dns1.convio.net. 5 A 74.123.155.132
dns2.p01.nsone.net. 2 A 198.51.45.1
dns3.p01.nsone.net. 2 A 198.51.44.65
dns4.p01.nsone.net. 2 A 198.51.45.65
dns1.p01.nsone.net. 2 AAAA 2620:4d:4000:6259:7:1:0:1
dns2.p01.nsone.net. 2 AAAA 2a00:edc0:6259:7:1:0:0:2
dns3.p01.nsone.net. 2 AAAA 2620:4d:4000:6259:7:1:0:3
dns4.p01.nsone.net. 2 AAAA 2a00:edc0:6259:7:1:0:0:4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0