Apex domains cannot have CNAME records.
Question and response
Question
dig guardedhost.com. NS
Answer
guardedhost.com. 3 NS ns2.guardeddns.net.
guardedhost.com. 3 NS ns1.guardedhost.com.
Authority
The response has no authority records.
Additional
ns1.guardedhost.com. 3 A 216.239.128.2
ns2.guardeddns.net. 3 A 204.10.136.2
ns1.guardedhost.com. 3 AAAA 2607:fe90:8000:0:0:0:0:2
ns2.guardeddns.net. 3 AAAA 2607:fe90:8001:0:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0