Mix everything except for the hazelnuts together in a small bowl and set aside.
Preheat the oven to 450*F. Warm a large, oven proof skillet over medium-high. Rub the flesh side of the salmon with the olive oil and season generously with salt and pepper.
Place the salmon, flesh side down, in the hot skillet. Season the other side of the salmon. Let the salmon cook until it has a deep brown crust.
Carefully flip the salmon. Turn the flame under the skillet off. Spread the mayo mixture evenly over the fish and sprinkle with the chopped hazelnuts. Gently pat the nuts in place. Put the skillet in the oven and roast the salmon until cooked thru, about 10 minutes.