Apex domains cannot have CNAME records.
Question and response
Question
dig umn.edu. NS
Answer
umn.edu. 5 NS ns-2.umn.edu.
umn.edu. 5 NS ns-3.umn.edu.
umn.edu. 5 NS ns-1.umn.edu.
Authority
The response has no authority records.
Additional
ns-1.umn.edu. 5 A 128.101.101.1
ns-2.umn.edu. 5 A 52.162.90.224
ns-3.umn.edu. 5 A 3.140.39.20
ns-1.umn.edu. 5 AAAA 2607:ea00:102:4801:0:0:0:53
ns-2.umn.edu. 5 AAAA 2a01:111:f100:1003:0:0:4134:36a1
ns-3.umn.edu. 5 AAAA 2600:1f16:4fe:2300:1d20:356b:4fc8:e9f1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0