I think the only way to be tornado resistant in a meaningful way is to go underground. An EF-5 can strip the blacktop off of a paved road.
The designs I have seen were essentially a concrete dome. I think they were supposed to be proof against even strong tornadoes. One link I saw mentioned Quonset huts as wind resistant. I guess that is a similar shape.
A search shows others looking at reinforced concrete walls and such. I imagine at least a concrete first floor would help and allow you to set up a safe room in the interior. I am sure it all costs more.
It also occurs to me that homes up there might not have the typical hurricane wind standards that are common down here. Mostly it is higher rated roof construction and the roof supports are strapped to the walls so the house can't be pulled apart so easily. Not going to stop a real big tornado, but might help.
https://www.foxblocks.com/blog/tornado-safe-homesThis one popped up on a search as a home made of concrete wall sections. I doubt it would survive undamaged, but it might not be completely wiped out like some pictured.
This link looks similar. Some sort of pre-fab foam wall sections with concrete poured in.
https://tornado-proof.com/
