I'm no expert when it comes to interpreting unbound logs, but I'm afraid yours above won't tell us much - it just shows the answer was drawn from unbound's cache:
But before you go about another attempt to log the actual recursion:
We currently have a very similar report, involving unbound and hub.docker.com, where resolution seems to have returned to normal:
If production.cloudflare.docker.com would be resolving again for you as well, that could suggest some transient issues with the configuration of authoritative DNS records, rather than unbound or Pi-hole.