Apex domains cannot have CNAME records.
Question and response
Question
dig metrooptic.com. NS
Answer
metrooptic.com. 5 NS ns2.metrooptic.com.
metrooptic.com. 5 NS ns3.metrooptic.com.
metrooptic.com. 5 NS ns1.metrooptic.com.
Authority
The response has no authority records.
Additional
ns1.metrooptic.com. 5 A 50.21.174.18
ns2.metrooptic.com. 5 A 192.172.250.8
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0