Apex domains cannot have CNAME records.
Question and response
Question
dig vaulting.io. NS
Answer
vaulting.io. 5 NS ns-616.awsdns-13.net.
vaulting.io. 5 NS ns-1687.awsdns-18.co.uk.
vaulting.io. 5 NS ns-324.awsdns-40.com.
vaulting.io. 5 NS ns-1483.awsdns-57.org.
Authority
The response has no authority records.
Additional
ns-324.awsdns-40.com. 3 A 205.251.193.68
ns-616.awsdns-13.net. 3 A 205.251.194.104
ns-1483.awsdns-57.org. 3 A 205.251.197.203
ns-1687.awsdns-18.co.uk. 3 A 205.251.198.151
ns-324.awsdns-40.com. 3 AAAA 2600:9000:5301:4400:0:0:0:1
ns-616.awsdns-13.net. 3 AAAA 2600:9000:5302:6800:0:0:0:1
ns-1483.awsdns-57.org. 3 AAAA 2600:9000:5305:cb00:0:0:0:1
ns-1687.awsdns-18.co.uk. 3 AAAA 2600:9000:5306:9700:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0