Apex domains cannot have CNAME records.
Question and response
Question
dig datto.com. NS
Answer
datto.com. 5 NS a22-66.akam.net.
datto.com. 5 NS a5-64.akam.net.
datto.com. 5 NS a1-24.akam.net.
datto.com. 5 NS a9-65.akam.net.
datto.com. 5 NS a10-65.akam.net.
datto.com. 5 NS a28-67.akam.net.
Authority
The response has no authority records.
Additional
a28-67.akam.net. 5 A 95.100.173.67
a28-67.akam.net. 5 AAAA 2600:1480:d800:0:0:0:0:43
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0