Make a quick pickle by thinly slicing the red onion and adding it to a bowl with the apple cider vinegar and a pinch of sea salt. Mix well, then set aside.
Roughly chop the artichokes and olives, leaving some whole for texture. Finely chop the parsley, including the stalks. Strip the mint leaves and roughly chop them. Add everything to the bowl with the onions.
Drain the butter beans and lentils, then add them to the bowl.
Warm the olive oil in a small pan. Add the za’atar and heat until fragrant. Stir in the garlic and cook briefly, then remove from the heat and allow to cool.
Once cooled, combine the oil with the sumac, lemon juice, and a pinch of salt in a jar. Seal and shake well.
Pour the dressing over the salad and toss to coat evenly.
Store in an airtight container in the fridge for up to three days.