Jamie serves this on a big platter, and made coriander salsa verde. You have to admit that his looks very pretty! I don't really like coriander, and was only making the dish for 3 people, which didn't really warrant a platter.
The salsa verde (my version) was a simple job for my food processor. Basil, mint, oil, red wine vinegar, capers and pepper. Pulse until done.
Cooking tuna doesn't really require much more effort - except you need to remember to marinate the tuna early enough, which I did. Then it was a simple matter of pan frying the tuna, blanching some greens and serving it with the salsa verde so it looks pretty on the plate as a single serve.
I (unashamedly) did the restaurant thing of stacking the tuna on the veg, which makes it practically impossible to eat, but sure looks good.