This is a dish to exploit the meatiness and sweet flavour of tuna. Best made if you have a ribbed iron grilling pan - but you can still do it if you don't have one. In this straightforward recipe, all the flavours help each other along, the colours are nice and there are some zingy sweet-sour notes played by the vinegar, lime and sugar.
4tbsp olive oil
4 shallots, finely chopped
1 red pepper and 1 yellow pepper, stem, ribs and seeds removed
1tbsp red wine vinegar
1 firm dark green lime, grated rind (no pith) and 2tsp juice
4 firm, ripe tomatoes, peeled, seeded and diced
salt and freshly ground black pepper
4 tuna steaks, weighing about 175g each
about 16 basil leaves, torn up
Heat half the oil in a medium saucepan and soften the shallots in it for 5 minutes. Cut the peppers into 1cm dice, add to the pan and cook gently, covered, for 10 minutes. Add the vinegar, lime rind, lime juice and sugar. Cook a further 5 minutes, uncover and let the liquid evaporate. This should only take 1-2 minutes. Add the tomatoes and cook under the lid for a further 2 minutes. Remove from the heat and season lightly with salt. You can make this ahead up to this point.
Meanwhile, heat the grilling pan to very hot. Brush the steaks with some of the remaining oil, season with salt and pepper, and cook for a couple of minutes each side, depending on how thick they are. This would be sufficient for a thickness of 15mm. Tuna is much better cooked rare, like (beef) steak.
Have the sauce very hot and stir in the basil leaves. Place a tuna steak on each of 4 plates and pour the sauce around, finishing off with the remaining olive oil.
Plain pasta tossed in olive oil would be good with this.