Prep Salmon: Pat salmon dry and season both sides with salt, pepper, and oregano.
Sear: Heat oil in a skillet over medium-high. Cook salmon 4-5 mins skin-side down, flip, and cook 2-3 mins more.
Rest: Remove salmon from pan and let rest for 5 minutes, then flake into large chunks.
Whisk Dressing: Combine all vinaigrette ingredients in a jar and shake until emulsified.
Assemble: Toss greens, cucumber, tomatoes, and onion in a bowl with half the dressing.
Serve: Top with salmon chunks, remaining dressing, and fresh parsley.