checkout.shopify.com has no CNAME records.
Question and response
Question
dig checkout.shopify.com. NS
Answer
The response has no answer records.
Authority
shopify.com. 1514 SOA gold.foundationdns.com. dns.cloudflare.com. 2397052600 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0