Sweet and sour tuna with onions (Tonno in agrodolce)

1. Peel the red onions and slice them into thin half-moons.

2. In a frying pan, cook the onions in 2 tablespoons of olive oil over medium heat for 10-12 minutes until soft and translucent; then sprinkle with the sugar, pour in the wine vinegar and bubble for 3-4 minutes until the liquid turns syrupy.

3. Pat the tuna steaks dry, season with salt and pepper and dust both sides lightly with flour.

4. Heat the remaining oil in another pan until very hot and sear the tuna for 1-2 minutes per side, so it browns outside but stays pink inside.

5. Place the tuna on a platter, pile the sweet and sour onions on top with their juices and scatter with roughly torn mint leaves.

6. Serve warm, lukewarm or even at room temperature - in Sicily it's often made the day before so the flavours can meld.

Tip: Tuna dries out easily: cooked right through it tastes like the tinned kind - don't be afraid to leave it pink.