Apex domains cannot have CNAME records.
Question and response
Question
dig rackanddata.com. NS
Answer
rackanddata.com. 5 NS authns2.rackanddata.com.
rackanddata.com. 5 NS authns1.rackanddata.com.
Authority
The response has no authority records.
Additional
authns1.rackanddata.com. 5 A 206.126.94.2
authns2.rackanddata.com. 5 A 98.143.96.171
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0