Thinly slice the onion and add to a large bowl, toss together with the kosher salt, lemon juice, and lemon zest. Set aside.
Drain and rinse the beans, roughly chop the olives, finely mince the herbs, and add everything to the bowl of onions.
In a pan, add the olive oil and garlic, and sauté on medium heat until the garlic just begins to brown. Remove from heat and sprinkle in the za’atar, sumac, and cumin.
Pour the marinade over the salad and toss together. Adjust for salt as needed.
Let the salad marinate for about 2 hours before serving, or enjoy it fresh.