Pat the salmon fillet dry with a paper towel and season both sides with sea salt, black pepper, and dried oregano.
Heat the extra virgin olive oil in a non-stick skillet over medium-high heat.
Place the salmon in the skillet skin-side down and sear for 4-5 minutes until the skin is crispy, then flip and cook for another 3-4 minutes until cooked through.
While the salmon cooks, whisk together the fresh lemon juice and Dijon mustard in a small bowl to create the dressing.
In a large mixing bowl, combine the cooked quinoa, baby spinach, diced cucumber, halved cherry tomatoes, and finely minced red onion.
Pour the dressing over the quinoa mixture and toss thoroughly to coat the vegetables and grains.
Transfer the salad to a serving plate and top with the warm pan-seared salmon fillet.
Garnish with freshly chopped parsley and an extra squeeze of lemon if desired.