Apex domains cannot have CNAME records.
Question and response
Question
dig esnet.com. NS
Answer
esnet.com. 4 NS ns1.esnet.com.
esnet.com. 4 NS ns3.esnet.com.
esnet.com. 4 NS ns2.esnet.com.
esnet.com. 4 NS ns4.esnet.com.
Authority
The response has no authority records.
Additional
ns1.esnet.com. 4 A 208.38.164.130
ns2.esnet.com. 4 A 216.139.200.132
ns3.esnet.com. 4 A 208.38.150.39
ns4.esnet.com. 4 A 76.10.200.4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0