The guest should be allowed to decide whether a fresh fish tartare is served completely raw or "aller et retour".
Many like toasty flavors and still a raw cold interior.
A standard burner or a crème brûlée burner is sufficient for scorching.
https://videos.files.wordpress.com/N4T7f1vr/lachstatar-abflaemmen_hd.mp4
The scarfing technique can also be used for tataki, salmon fillet and other foods.