Apex domains cannot have CNAME records.
Question and response
Question
dig md02.com. NS
Answer
md02.com. 5 NS nsm1.tckops.net.
md02.com. 5 NS nsm0.tckops.net.
md02.com. 5 NS nsm4.tckops.net.
md02.com. 5 NS nsm3.tckops.net.
md02.com. 5 NS nsm2.tckops.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0