Apex domains cannot have CNAME records.
Question and response
Question
dig kolo.net. NS
Answer
kolo.net. 5 NS ans1.nd.kolo.net.
kolo.net. 5 NS puck.nether.net.
kolo.net. 5 NS dns42.cloudns.net.
kolo.net. 5 NS dns44.cloudns.net.
kolo.net. 5 NS ns-he.kolo.net.
kolo.net. 5 NS ns.kolo.net.
Authority
The response has no authority records.
Additional
ns.kolo.net. 5 A 216.218.215.20
ans1.nd.kolo.net. 5 A 74.123.227.136
puck.nether.net. 5 A 204.42.254.5
ns-he.kolo.net. 5 A 216.218.215.2
puck.nether.net. 5 AAAA 2602:fe55:5:0:0:0:0:5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0