Apex domains cannot have CNAME records.
Question and response
Question
dig dattobackup.com. NS
Answer
dattobackup.com. 4 NS ns2.dattobackup.com.
dattobackup.com. 4 NS ns3.dattobackup.com.
dattobackup.com. 4 NS ns1.dattobackup.com.
Authority
The response has no authority records.
Additional
ns1.dattobackup.com. 4 A 8.34.181.249
ns2.dattobackup.com. 4 A 192.171.96.243
ns3.dattobackup.com. 4 A 192.171.96.241
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0