There's really no need for a certificate on an onion name - onion names are already the hash of your public key. Tor validates everything for that already and i

There's really no need for a certificate on an onion name - onion names are already the hash of your public key. Tor validates everything for that already and if someone else can compromise your onion name, they could just produce a certificate for it anyways. Unlike with regular http vs SSL, Tor provides confidentiality, integrity and host authentication integrated simply by connecting to the right name.