Apex domains cannot have CNAME records.
Question and response
Question
dig vercel-dns-016.com. NS
Answer
vercel-dns-016.com. 4 NS ns3.vercel-dns-016.com.
vercel-dns-016.com. 4 NS ns2.vercel-dns-016.com.
vercel-dns-016.com. 4 NS ns1.vercel-dns-016.com.
vercel-dns-016.com. 4 NS ns4.vercel-dns-016.com.
Authority
The response has no authority records.
Additional
ns1.vercel-dns-016.com. 4 A 205.251.196.231
ns2.vercel-dns-016.com. 4 A 205.251.194.173
ns3.vercel-dns-016.com. 4 A 205.251.193.82
ns4.vercel-dns-016.com. 4 A 205.251.198.187
ns1.vercel-dns-016.com. 4 AAAA 2600:9000:5304:e700:0:0:0:1
ns2.vercel-dns-016.com. 4 AAAA 2600:9000:5302:ad00:0:0:0:1
ns3.vercel-dns-016.com. 4 AAAA 2600:9000:5301:5200:0:0:0:1
ns4.vercel-dns-016.com. 4 AAAA 2600:9000:5306:bb00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0