Cook the buckwheat groats: Place buckwheat in a medium pot, pour in boiling water or broth. Add olive oil, stir, cover the pot and bring to a boil. Cook for 15 minutes over low heat. Remove the pot from the heat, uncover and leave for 10-15 minutes. After this time, fluff up with a fork, and season with salt and pepper to taste.
Peel the oranges and cut into slices. Cut the beetroots into slices*.
Rinse and dry the arugula (preferably in a salad spinner).
Mix the ingredients for the sauce together. The fastest way to do this is to pour them into a small jar, close the lid, and shake well. You can also mix it in a food processor - the sauce will be thicker and creamier.
Toast the nuts on a dry pan until slightly brown and fragrant. Immediately transfer to a plate as they can burn quickly.
Spread cooked buckwheat on a plate, put arugula leaves on top, then arrange beetroot and orange slices, crumble the feta cheese over the salad. Sprinkle with toasted haselnuts and pour over the sauce.
Enjoy!