Apex domains cannot have CNAME records.
Question and response
Question
dig cloudflare.COM. NS
Answer
cloudflare.COM. 5 NS ns4.cloudflare.COM.
cloudflare.COM. 5 NS ns6.cloudflare.COM.
cloudflare.COM. 5 NS ns7.cloudflare.COM.
cloudflare.COM. 5 NS ns3.cloudflare.COM.
cloudflare.COM. 5 NS ns5.cloudflare.COM.
Authority
The response has no authority records.
Additional
ns3.cloudflare.com. 5 A 162.159.0.33
ns3.cloudflare.com. 5 A 162.159.7.226
ns4.cloudflare.com. 5 A 162.159.1.33
ns4.cloudflare.com. 5 A 162.159.8.55
ns5.cloudflare.com. 5 A 162.159.2.9
ns5.cloudflare.com. 5 A 162.159.9.55
ns6.cloudflare.com. 5 A 162.159.3.11
ns6.cloudflare.com. 5 A 162.159.5.6
ns7.cloudflare.com. 5 A 162.159.4.8
ns7.cloudflare.com. 5 A 162.159.6.6
ns3.cloudflare.com. 5 AAAA 2400:cb00:2049:1:0:0:a29f:21
ns3.cloudflare.com. 5 AAAA 2400:cb00:2049:1:0:0:a29f:7e2
ns4.cloudflare.com. 5 AAAA 2400:cb00:2049:1:0:0:a29f:121
ns4.cloudflare.com. 5 AAAA 2400:cb00:2049:1:0:0:a29f:837
ns5.cloudflare.com. 5 AAAA 2400:cb00:2049:1:0:0:a29f:209
ns5.cloudflare.com. 5 AAAA 2400:cb00:2049:1:0:0:a29f:937
ns6.cloudflare.com. 5 AAAA 2400:cb00:2049:1:0:0:a29f:30b
ns6.cloudflare.com. 5 AAAA 2400:cb00:2049:1:0:0:a29f:506
ns7.cloudflare.com. 5 AAAA 2400:cb00:2049:1:0:0:a29f:408
ns7.cloudflare.com. 5 AAAA 2400:cb00:2049:1:0:0:a29f:606
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0