1. Preheat your grill pan over medium-high heat.
2. Season the salmon fillets with salt and pepper.
3. Grill the salmon for about 4-5 minutes on each side, or until fully cooked. Set aside to cool slightly.
4. In a large mixing bowl, combine the mixed greens, cherry tomatoes, cucumber, red onion, and feta cheese.
5. In a small bowl, whisk together the olive oil, lemon juice, Dijon mustard, minced garlic, salt, and pepper to make the dressing.
6. Flake the grilled salmon into large chunks and add to the salad.
7. Drizzle the dressing over the salad and toss gently to combine.
8. Serve immediately.