Preheat your oven to 200ºC/Fan 180ºC/Gas 6. Halve your nectarines. Use a teaspoon to scoop out the stones. Set the nectarines in a roasting dish, cut side up. Roast 15 mins or till everything is tender, sticky and sweet.
Halve, peel and thinly slice your onion. Toss with 1 tbsp oil and a pinch of salt. Arrange around your nectarines or in a separate dish and cook for 10 mins (i.e. add them after the nectarines have been in the oven for 5 mins).
Blend 4 of the nectarine halves with the ras el hanut and honey till smooth. Taste. Add more honey or ras el hanut, as needed. Gently mix the watercress with the dressing.
Slice the remaining nectarines. Strip the mint leaves from the stalks. Gently mix the nectarine slices and mint into the salad.
Set a frying pan over medium heat. Add the almonds. Toast till just golden. Scatter the roasted onion slices and toasted almonds over the top of the salad and serve.