Heat oven to 220C/fan 200C/gas 7 and
put in a roasting tin to heat up. Put the tuna
in a shallow dish with half the oil, two-thirds
of the garlic and leaves from 1 sprig of thyme.
Leave to marinate while you cook the veg.
Put the potatoes, peppers, onion and chilli
into the roasting tin with the remaining oil,
toss to coat, then roast for 20 mins. The
potatoes should be tender or very nearly
there. If not, give them another 5 mins (the
cooking time can depend on the variety of
potato). Add the remaining garlic and thyme
to the pan, let them sizzle, stir in the tomatoes,
then cook for 5 mins more until the sauce
has reduced a little. Season to taste.
With a few mins to go, heat a griddle or
frying pan, wipe most of the garlic marinade
off the fish with kitchen paper, season, then
sear for 1 min each side for medium or longer
if you prefer. Serve on top of the veg.