Place hazelnuts on a sheet pan lined with parchment paper, roast for 10 to 12 minutes or until just browned and fragrant, cool completely. Rub off any dark skin still left on hazelnuts and discard skins.
In a food processor place hazelnuts, sesame seeds, za'atar, cumin, coriander and salt and pepper. Pulse to combine but do not over pulse and make paste, you are looking for breadcrumb consistency.
Place salmon on a sheet pan lined with parchment paper, add a layer of dukkah and pat to ensure adhesion. Bake 12 to 15 minutes or until fully cooked.
Season to taste as needed. Store dukkah in an airtight container on the counter, it will keep for at least 2 weeks. Dukkah is also great on salads.