Apex domains cannot have CNAME records.
Question and response
Question
dig i.root-servers.org. NS
Answer
i.root-servers.org. 5 NS nnb.netnod.se.
i.root-servers.org. 5 NS nnu.netnod.se.
i.root-servers.org. 5 NS nna.netnod.se.
i.root-servers.org. 5 NS nnp.netnod.se.
Authority
The response has no authority records.
Additional
nna.netnod.se. 5 A 194.58.192.133
nnb.netnod.se. 5 A 194.58.193.133
nnp.netnod.se. 5 A 194.58.198.133
nnu.netnod.se. 5 A 185.42.137.133
nna.netnod.se. 5 AAAA 2a01:3f1:33:8000:0:0:0:53
nnb.netnod.se. 5 AAAA 2a01:3f1:433:8000:0:0:0:53
nnp.netnod.se. 5 AAAA 2a01:3f1:3033:8000:0:0:0:53
nnu.netnod.se. 5 AAAA 2a01:3f0:400:8000:0:0:0:33
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0