Thinly slice the red onion. Mix the onions, white wine vinegar and a pinch of sea salt in a bowl. Gently massage the onions with your hands for a few seconds. Set it aside to macerate for about 15 minutes while you prepare the salad.
To make the yoghurt dressing, add the lime zest and one tablespoon of lime juice to a bowl with the remaining dressing ingredients and whisk until well combined. Add ground sea salt and black pepper to taste and set aside until needed. The dressing should be creamy and thick yet pourable. Add a teaspoon of water if it is too thick.
Place the quartered artichoke hearts in a large mixing bowl and add the herbs, reserving some to scatter on top. If you are using canned artichokes in brine, add a tablespoon of olive oil to coat the artichokes.
Remove the onions from the vinegar, gently squeeze out any excess vinegar and add to the artichoke mix.
Add most of the walnuts, reserving a few to scatter on top.
Place the arugula leaves in a serving bowl. Top it with the artichoke mix. And spoon over a few dollops of lime yoghurt dressing. Serve any remaining yoghurt dressing on the side.
Crumble over the feta, and scatter the reserved walnuts and herbs. Finish with a final drizzle of olive oil and a sprinkling of salt flakes.