Sesame & seaweed crusted tuna

I’m passionate about tuna and when I find a piece that is fantastically fresh I’m loath to cook it for more than a few seconds. Unfortunately the kind of tuna you  find in most supermarkets is rarely fresh enough and just wouldn’t do for this kind of recipe. Instead, seek out a good fishmonger and ask for ‘sashimi grade tuna’. Let them know that you plan to serve it raw. The sesame and seaweed seasoning in this recipe is often sold wherever you can buy sushi-making kits and adds a lovely savoury flavour to the tuna. If you can’t track any down, simply use sesame seeds instead for an equally delicious variation.