To make the dressing, put all the ingredients in a small bowl, season with salt and freshly
ground black pepper and whisk to combine.
Cut the lamb fillets in half and season with freshly ground black pepper. Lightly spray the
olive oil in a frying pan over high heat and cook the lamb for 3-4 minutes, or until browned,
turning once or twice. Season with salt and remove from the heat.
Peel the oranges and grapefruit. removing all the white pith. Holding them over a bowl to catch
the juice, segment them by using a small, sharp knife to cut between the membranes. Put the
segments in the bowl with the juices.
Cut the lamb on the diagonal into 2.5cm / 1 in thick slices and add to the bowl, along with the
watercress and red onion. Pour the dressing over the salad and lightly toss to coat.