Apex domains cannot have CNAME records.
Question and response
Question
dig 3m.com. NS
Answer
3m.com. 5 NS a.ns.3m.com.
3m.com. 5 NS b.ns.3m.com.
Authority
The response has no authority records.
Additional
a.ns.3m.com. 5 A 162.159.8.174
b.ns.3m.com. 5 A 173.245.58.19
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0