Apex domains cannot have CNAME records.
Question and response
Question
dig zayo.us. NS
Answer
zayo.us. 5 NS ns1.zayo.us.
zayo.us. 5 NS ns2.zayo.us.
Authority
The response has no authority records.
Additional
ns1.zayo.us. 5 A 64.125.228.5
ns2.zayo.us. 5 A 64.125.226.5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0