How to use DNS-over-TLS with BIND9 forwarders

BIND9 v9.18 improves support for DNS-over-TLS (DoT) and DNS-over-HTTPS (DoH). However, while the [docs](https://bind9.readthedocs.io/en/v9_18_11/) explain how to use TLS for the server part, it does not reveal how to enable DNS-over-TLS for query forwarding. Does BIND9 v9.18 support it? How does the config snippet need to be tweaked to use DoT for the forwarders?

options {
        […]
        forwarders {
                // Forward to Cloudflare public DNS resolver
                1.1.1.1;
                1.0.0.1;
        };
        […]
}

Simply adding port 853 and expecting some magic to happen does not seem to be enough.