Mediterranean Tuna Sandwich with Pickled Red Onions

In a small bowl, whisk together the olive oil and red wine vinegar. Add the sliced red onion and let it marinate while you prepare everything else - this quick pickle will cut through the richness beautifully.

Lay out your bread slices. Brush the bottom pieces lightly with some of the oil and vinegar mixture, then layer on the pickled onions.

Scatter the capers and halved olives over the onions, then break up the tuna with a fork and distribute it evenly. (Don't drain the tuna too thoroughly - you want some of that good olive oil)

Layer on the tomato slices and greens, then drizzle lightly with the remaining oil and vinegar mixture before topping with the second bread slice.

Press the sandwich together gently and let it rest for 5 minutes - this allows all the flavors to meld and the bread to absorb some of the lovely juices. Serve with plenty of napkins.