In a large mixing bowl, combine the chopped lettuce, flaked salmon, cucumber, red bell peppers, red onions, avocado, and parsley. Toss gently to ensure even distribution of all the ingredients.
In a mason jar, combine the lemon juice and olive oil. Season with salt and freshly ground black pepper. Secure the lid and shake vigorously until the dressing is well emulsified.
Sample the dressing to ensure the seasoning is to your preference, then drizzle it over the salad. Toss the salad gently to coat the ingredients with the dressing. Serve immediately and enjoy the fresh, vibrant flavors of this nutritious dish!