Apex domains cannot have CNAME records.
Question and response
Question
dig azurestaticapps.net. NS
Answer
azurestaticapps.net. 4 NS ns1-03.azure-dns.com.
azurestaticapps.net. 4 NS ns3-03.azure-dns.org.
azurestaticapps.net. 4 NS ns2-03.azure-dns.net.
azurestaticapps.net. 4 NS ns4-03.azure-dns.info.
Authority
The response has no authority records.
Additional
ns1-03.azure-dns.com. 4 A 13.107.236.3
ns3-03.azure-dns.org. 4 A 204.14.183.3
ns4-03.azure-dns.info. 4 A 208.84.5.3
ns1-03.azure-dns.com. 4 AAAA 2603:1061:0:700:0:0:0:3
ns3-03.azure-dns.org. 4 AAAA 2a01:111:4000:700:0:0:0:3
ns4-03.azure-dns.info. 4 AAAA 2620:1ec:bda:700:0:0:0:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0