Apex domains cannot have CNAME records.
Question and response
Question
dig grumpyminx.com. NS
Answer
grumpyminx.com. 3 NS ns3.grumpyminx.com.
grumpyminx.com. 3 NS ns1.grumpyminx.com.
grumpyminx.com. 3 NS ns2.grumpyminx.com.
Authority
The response has no authority records.
Additional
ns1.grumpyminx.com. 3 A 178.63.67.56
ns2.grumpyminx.com. 3 A 77.104.162.218
ns3.grumpyminx.com. 3 A 65.21.91.95
ns1.grumpyminx.com. 3 AAAA 2a01:4f8:121:1061:0:0:0:2
ns2.grumpyminx.com. 3 AAAA 2a02:8010:d015:0:0:0:0:123
ns3.grumpyminx.com. 3 AAAA 2a01:4f9:3b:4384:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0