Mix the olive oil, garlic, soy sauce and pepper. Put the tuna steaks in a dish and pour the marinade over them, turning to coat.
Leave for 30 minutes covered, somewhere cool.
Heat a griddle pan until it’s really hot. Lift the tuna out of the marinade and gently shake off the excess.
Griddle the tuna for about one minute each side (this gives you a moist interior that is quite raw in the centre).
A Change of Appetite: where delicious meets healthy by Diana Henry, Photography by Laura Edwards, published by Mitchell Beazley, £20, www.octopusbooks.co.uk