Apex domains cannot have CNAME records.
Question and response
Question
dig hotmail.com. NS
Answer
hotmail.com. 5 NS ns3-205.azure-dns.org.
hotmail.com. 5 NS ns4-205.azure-dns.info.
hotmail.com. 5 NS ns1-205.azure-dns.com.
hotmail.com. 5 NS ns2-205.azure-dns.net.
Authority
The response has no authority records.
Additional
ns2-205.azure-dns.net. 3 A 150.171.21.205
ns3-205.azure-dns.org. 3 A 204.14.183.205
ns4-205.azure-dns.info. 3 A 208.84.5.205
ns2-205.azure-dns.net. 3 AAAA 2620:1ec:8ec:700:0:0:0:cd
ns3-205.azure-dns.org. 3 AAAA 2a01:111:4000:700:0:0:0:cd
ns4-205.azure-dns.info. 3 AAAA 2620:1ec:bda:700:0:0:0:cd
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0