Cut the onion into quarter rings and marinate (as I usually do: put the chopped onion in a deep bowl, add a generous pinch of salt and sugar, about 3 tbsp. l. vinegar, pour boiling water, mix, cover the bowl and let stand for 30 minutes. Then drain the marinade and let the excess liquid drain from the onion).
Boil the potatoes and carrots and let them cool. Cut into pieces.
Add the pickled onion.
Add the arugula leaves.
Coarsely chopped coriander. Season with salt and black pepper to taste.
Crush the coriander seeds and grind them a little in a mortar.
Add the crushed coriander to the rest of the ingredients, season the salad with olive oil and serve!