Apex domains cannot have CNAME records.
Question and response
Question
dig iomartcloud.com. NS
Answer
iomartcloud.com. 5 NS iphicles.iomart.com.
iomartcloud.com. 5 NS hebe.iomart.com.
iomartcloud.com. 5 NS heracles.iomart.com.
Authority
The response has no authority records.
Additional
hebe.iomart.com. 5 A 74.117.184.100
heracles.iomart.com. 5 A 62.128.193.135
iphicles.iomart.com. 5 A 84.22.161.172
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0