What is the rawest a restaurant can get to cooking a steak?

 As raw as possible?

Crude.

Yes, you read it right. Crude.

However, if you decide to go for it, make sure you go to a high-end restaurant… one that is known for having exclusive access to top-quality meat. Such a restaurant will literally know not only the actual freshness of the meat, but also its provenance, how it has been treated, cared for and even raised. It will have the best possible food hygiene practices, and you will most likely not get sick from eating it.

Otherwise, most quality restaurants would cook a steak "rare as possible" as " blue rare ". It is essentially a barely cooked meat, with a semi-roasted outer layer.

As you can see in the image, the meat has hardly touched heat. The exterior has the least possible cooking to be healthy consumption. It's not to my liking, but I know a few people who love it that way, describing it when they order it as " still mooing ".