Apex domains cannot have CNAME records.
Question and response
Question
dig ctl.one. NS
Answer
ctl.one. 5 NS ns4.level3.net.
ctl.one. 5 NS ns3.level3.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0