what is flash-seared food?

It is cooked in a hot pan so that the outside is cooked and brown and the inside is pretty much raw.

Tuna is now served this way -- ugh -- I don't like it but people who do insist it is the only way to eat tuna.

You cook it in a frying pan at a very hot temperature for a very short period of time in order to get a nice brown color on the outside of the meat but very rare in the middle

Next to raw meat that's about it .