In a small bowl, whisk together olive oil, lemon juice, orange juice, Dijon mustard, garlic, salt, and pepper until smooth and well combined.
Pour the prepared dressing into the bottom of a clean mason jar, making sure it fully covers the base.
Add the firm vegetables like cucumber, carrots, red onion, and bell peppers into the jar. Press gently so they sit evenly in the dressing.
Add the cherry tomatoes on top of the vegetable layer, spreading them evenly.
Add the flaked salmon, making sure it is evenly distributed for balanced flavor in every bite.
Add the chopped romaine lettuce as the final top layer. Keep it loose and do not press down.
Seal the jar tightly with a lid and store it in the refrigerator for up to three days.
When ready to eat, shake the jar well to mix the dressing with the salad or pour into a bowl and toss gently before serving.