Place the salmon filets in shallow bowl, toss well with lemon juice, zest, oil and salt. Let rest 15 minutes. Meanwhile heat a skillet to medium/high heat. Place the salmon skin side down and cook 2-3 minutes. Shake the pan gently so salmon does not stick. Reduce the heat to medium cover and cook until salmon is cooked through, 3 to 4 minutes more. The skin should be crisp and flesh medium. Cook an additional 3 minutes for well done. Remove from heat and let rest and cool to room temp. In mixing bowl add aruguls, lemon juice and zest and toss. Add oil, red onion and walnuts. Toss and place handful sized portion on serving plate. Top with salmon, serve and enjoy!