Best bet so far is to run your own relay and strip the forwarding data.
Discussion
I suppose to include here, you are often nost just trusting the relay hoster, but often CloudFlare for observing your plaintext traffic, IPs, and so on, or whatever datacenter/hosting provider the relay owner is using as well. I can't imagine most relay owners are hosting their relays from their home networks.
These are often American or European companies, and therefore less likely to be a threat to me, personally, than individual nutjobs.
Pick your poison.