Place the lamb in a resealable plastic bag orange rind, olive oil, thyme and za’atar. Refrigerate for 2-3 hours or leave overnight.
Preheat a non-stick pan to moderately hot. Cook one side of lamb until the first sign of moisture appears, then turn once and cook until done to your liking. Test for doneness with tongs. Rare is soft when pressed, medium is springy and well done is very firm.
Remove lamb from the heat, loosely cover and allow to rest for 3 minutes. While the lamb rests prepare the salad. Slice the lamb on a slight angle into 1-2cm thick slices and toss with the salad.
To make salad cut away the thick skin and pith from the oranges and segment or dice the flesh. Place in a bowl with the dates, rocket or baby salad leaves, olives, sliced red onion, thyme, chilli, olive oil and vinegar. Season well with salt and pepper.