Put the marinade ingredients into a large bowl. Add the lamb strips and gently stir to combine. Cover and set aside for 15 mins or in the fridge for longer, if time allows.
To prepare the onion relish, put all the ingredients into a large bowl. Cover and set aside for 10-15 mins.
To prepare the feta whip, put all the ingredients except the herbs in a large bowl. Using a stick blender, whizz together until combined (or you can use a mini-blender if you prefer). Stir through herbs and set aside until required.
Heat a large non-stick pan over moderate heat. Add the lamb and pan fry for 2-3 mins, tossing continuously.
Warm the flatbreads or pitta. Spread each flatbread with a little of the feta whip, the lamb, and the red onion relish. Serve with a side salad.