In a large mixing bowl, combine the flaked salmon, red bell peppers, red onions, cucumber, avocado, lettuce, and parsley. Toss gently to mix all the ingredients together.
In a mason jar, combine the freshly squeezed lemon juice, salt, and black pepper. Secure the lid and shake well, then slowly stream in the olive oil while whisking until fully emulsified.
Taste the dressing for seasoning, then drizzle it over the salad. Toss to coat evenly. Serve and enjoy immediately!