Apex domains cannot have CNAME records.
Question and response
Question
dig ai. NS
Answer
ai. 5 NS v0n0.nic.ai.
ai. 5 NS v2n0.nic.ai.
ai. 5 NS v0n2.nic.ai.
ai. 5 NS v0n3.nic.ai.
ai. 5 NS v0n1.nic.ai.
ai. 5 NS v2n1.nic.ai.
Authority
The response has no authority records.
Additional
v0n0.nic.ai. 143645 A 199.115.152.1
v0n1.nic.ai. 143645 A 199.115.153.1
v0n2.nic.ai. 143645 A 199.115.154.1
v0n3.nic.ai. 143645 A 199.115.155.1
v2n0.nic.ai. 143645 A 199.115.156.1
v2n1.nic.ai. 143645 A 199.115.157.1
v0n0.nic.ai. 143645 AAAA 2001:500:a0:0:0:0:0:1
v0n1.nic.ai. 143645 AAAA 2001:500:a1:0:0:0:0:1
v0n2.nic.ai. 143645 AAAA 2001:500:a2:0:0:0:0:1
v0n3.nic.ai. 143645 AAAA 2001:500:a3:0:0:0:0:1
v2n0.nic.ai. 143645 AAAA 2001:500:a4:0:0:0:0:1
v2n1.nic.ai. 143645 AAAA 2001:500:a5:0:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0