Apex domains cannot have CNAME records.
Question and response
Question
dig netlifydns.com. NS
Answer
netlifydns.com. 3 NS ns03.netlifydns.com.
netlifydns.com. 3 NS ns04.netlifydns.com.
netlifydns.com. 3 NS ns01.netlifydns.com.
netlifydns.com. 3 NS ns02.netlifydns.com.
netlifydns.com. 3 NS dns1.p07.nsone.net.
netlifydns.com. 3 NS dns2.p07.nsone.net.
netlifydns.com. 3 NS dns3.p07.nsone.net.
netlifydns.com. 3 NS dns4.p07.nsone.net.
Authority
The response has no authority records.
Additional
ns01.netlifydns.com. 3 A 45.54.30.1
ns02.netlifydns.com. 3 A 45.54.30.65
ns03.netlifydns.com. 3 A 45.54.30.129
ns04.netlifydns.com. 3 A 45.54.30.193
ns01.netlifydns.com. 3 AAAA 2607:f740:e630:0:0:0:0:1
ns02.netlifydns.com. 3 AAAA 2607:f740:e630:4:0:0:0:1
ns03.netlifydns.com. 3 AAAA 2607:f740:e630:8:0:0:0:1
ns04.netlifydns.com. 3 AAAA 2607:f740:e630:c:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0