Looks like just DNS for the CNAME is broken.

    $ dig @1.1.1.1 stark-wisteria-rnbgkawldfk6gq7m8308ytts.herokudns.com A
    ...
    ;; OPT PSEUDOSECTION:
    ; EDNS: version: 0, flags:; udp: 1232
    ; OPT=15: 00 09 6e 6f 20 53 45 50 20 6d 61 74 63 68 69 6e 67 20 74 68 65 20 44 53 20 66 6f 75 6e 64 20 66 6f 72 20 68 65 72 6f 6b 75 64 6e 73 2e 63 6f 6d 2e ("..no SEP matching the DS found for herokudns.com.")
    ;; QUESTION SECTION:
    ;stark-wisteria-rnbgkawldfk6gq7m8308ytts.herokudns.com. IN A

I wonder if there is any way to get out an IP address of the Heroku router we were assigned to that we can use in place of the CNAME.

Might be in the logs somewhere, or in Cloudflare somewhere?