Cut the tuna into slices and then either grill or fry in a non-stick pan. Season well with salt. Once cooked, drizzle some olive oil over the tuna.
Peel the oranges and the grapefruits, removing all the pith. Remove the segments and squeeze the juice in to a separate bowl. Set aside.
Season the rocket with the citrus juice, pepper and salt.
Serve the tuna on a bed of rocket with some segments arranged around it.
«To enable you to cut the tuna into fine slices, place it in the fridge for a well. This will harden it a little and making slicing neatly easier.»