Wash and dry your lettuce. Cut or tear into bite-sized pieces.
Arrange the mango and pickled onions over the lettuce leaves.
Pat your salmon as dry as possible with paper towels.
Place a stainless steel pan or cast iron skillet over high heat. Once hot, turn down to medium heat. Season the salmon with salt, add a bit of oil to the pan, and place the salmon in the pan skin-side down.
Cook for about 4 minutes per side, depending on the thickness of your fillets.
Use an instant-read thermometer to determine when the salmon is ready to take off of the heat. The salmon should flake easily with a fork, have a somewhat pink interior, and read 120 degrees Fahrenheit for medium-rare. Cook for a few minutes longer if you prefer more cooked salmon.
Let the salmon rest for a few minutes, then transfer to the salad, skin-side up.
Taste for seasoning, drizzle with dressing, and serve.