Apex domains cannot have CNAME records.
Question and response
Question
dig root-servers.net. NS
Answer
root-servers.net. 1 NS c.root-servers.net.
root-servers.net. 1 NS j.root-servers.net.
root-servers.net. 1 NS m.root-servers.net.
root-servers.net. 1 NS d.root-servers.net.
root-servers.net. 1 NS g.root-servers.net.
root-servers.net. 1 NS f.root-servers.net.
root-servers.net. 1 NS l.root-servers.net.
root-servers.net. 1 NS b.root-servers.net.
root-servers.net. 1 NS i.root-servers.net.
root-servers.net. 1 NS h.root-servers.net.
root-servers.net. 1 NS a.root-servers.net.
root-servers.net. 1 NS e.root-servers.net.
root-servers.net. 1 NS k.root-servers.net.
Authority
The response has no authority records.
Additional
a.root-servers.net. 91864 A 198.41.0.4
b.root-servers.net. 91864 A 170.247.170.2
c.root-servers.net. 91864 A 192.33.4.12
d.root-servers.net. 91864 A 199.7.91.13
e.root-servers.net. 91864 A 192.203.230.10
f.root-servers.net. 91864 A 192.5.5.241
g.root-servers.net. 91864 A 192.112.36.4
h.root-servers.net. 91864 A 198.97.190.53
i.root-servers.net. 91864 A 192.36.148.17
j.root-servers.net. 91864 A 192.58.128.30
k.root-servers.net. 91864 A 193.0.14.129
l.root-servers.net. 91864 A 199.7.83.42
m.root-servers.net. 91864 A 202.12.27.33
a.root-servers.net. 91864 AAAA 2001:503:ba3e:0:0:0:2:30
b.root-servers.net. 91864 AAAA 2801:1b8:10:0:0:0:0:b
c.root-servers.net. 91864 AAAA 2001:500:2:0:0:0:0:c
d.root-servers.net. 91864 AAAA 2001:500:2d:0:0:0:0:d
e.root-servers.net. 91864 AAAA 2001:500:a8:0:0:0:0:e
f.root-servers.net. 91864 AAAA 2001:500:2f:0:0:0:0:f
g.root-servers.net. 91864 AAAA 2001:500:12:0:0:0:0:d0d
h.root-servers.net. 91864 AAAA 2001:500:1:0:0:0:0:53
i.root-servers.net. 91864 AAAA 2001:7fe:0:0:0:0:0:53
j.root-servers.net. 91864 AAAA 2001:503:c27:0:0:0:2:30
k.root-servers.net. 91864 AAAA 2001:7fd:0:0:0:0:0:1
l.root-servers.net. 91864 AAAA 2001:500:9f:0:0:0:0:42
m.root-servers.net. 91864 AAAA 2001:dc3:0:0:0:0:0:35
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0