Apex domains cannot have CNAME records.
Question and response
Question
dig mythic-beasts.com. NS
Answer
mythic-beasts.com. 5 NS ns3.mythic-beasts.com.
mythic-beasts.com. 5 NS ns1.mythic-beasts.com.
mythic-beasts.com. 5 NS ns2.mythic-beasts.com.
Authority
The response has no authority records.
Additional
ns1.mythic-beasts.com. 5 A 45.33.127.156
ns2.mythic-beasts.com. 5 A 93.93.128.67
ns3.mythic-beasts.com. 5 A 185.24.221.32
ns1.mythic-beasts.com. 5 AAAA 2600:3c00:e000:19:0:0:0:1
ns2.mythic-beasts.com. 5 AAAA 2a00:1098:0:80:1000:0:0:10
ns3.mythic-beasts.com. 5 AAAA 2a02:2770:11:0:21a:4aff:febe:759b
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0