Tip the buckwheat into a pan and cover with 250ml boiling water. Add a pinch of salt. Pop on a lid and bring to the boil. Simmer for 6 mins. Turn off the heat and let it sit for 2 mins, then drain off any excess liquid. Pop on a lid to keep warm.
Meanwhile, put half the basil in a mini processor. Roughly chop the ripest nectarine, discarding the stone. Add to the basil with 2 tbsp oil and 1 tbsp cold water. Season. Whizz till smooth. This is your dressing. No processor? Finely chop the basil and a nectarine. Crush with the back of a fork. Add the oil and mix together.
Cut the remaining nectarines into quarters. Put in a bowl with ½ tsp ras el hanut and ½ tbsp oil. Turn to mix.
Heat a griddle or frying pan for 2-3 mins till smoking hot. Add the nectarine wedges and griddle for 1-2 mins on each side till charred. Set aside on a plate.
Peel the onion. Slice it into wedges. Char in a griddle pan for 2-3 mins. Toss the buckwheat with the griddled onion, nectarine and basil dressing and 1 tsp ras el hanut in a large bowl. Add half the rocket and toss that through.
Arrange the remaining rocket on a serving platter. Spoon over the nectarine dressed buckwheat.
Top with the griddled nectarines and crumble over half the pack of feta. Add a pinch or two more of the ras el hanut if you wish. Garnish with the remaining basil. Serve.