Apex domains cannot have CNAME records.
Question and response
Question
dig microsoft. NS
Answer
microsoft. 5 NS dnsc.nic.microsoft.
microsoft. 5 NS dnsd.nic.microsoft.
microsoft. 5 NS dns1.nic.microsoft.
microsoft. 5 NS dns2.nic.microsoft.
microsoft. 5 NS dns3.nic.microsoft.
microsoft. 5 NS dnsa.nic.microsoft.
microsoft. 5 NS dnsb.nic.microsoft.
microsoft. 5 NS dns4.nic.microsoft.
Authority
The response has no authority records.
Additional
dns1.nic.microsoft. 149744 A 213.248.219.132
dns2.nic.microsoft. 149744 A 103.49.83.132
dns3.nic.microsoft. 149744 A 213.248.223.132
dns4.nic.microsoft. 149744 A 43.230.51.132
dnsa.nic.microsoft. 149744 A 156.154.100.3
dnsb.nic.microsoft. 149744 A 156.154.101.3
dnsc.nic.microsoft. 149744 A 156.154.102.3
dnsd.nic.microsoft. 149744 A 156.154.103.3
dns1.nic.microsoft. 149744 AAAA 2a01:618:403:0:0:0:0:132
dns2.nic.microsoft. 149744 AAAA 2401:fd80:403:0:0:0:0:132
dns3.nic.microsoft. 149744 AAAA 2a01:618:407:0:0:0:0:132
dns4.nic.microsoft. 149744 AAAA 2401:fd80:407:0:0:0:0:132
dnsa.nic.microsoft. 149744 AAAA 2001:502:ad09:0:0:0:0:3
dnsb.nic.microsoft. 149744 AAAA 2001:502:2eda:0:0:0:0:3
dnsc.nic.microsoft. 149744 AAAA 2610:a1:1009:0:0:0:0:3
dnsd.nic.microsoft. 149744 AAAA 2610:a1:1010:0:0:0:0:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0