In separate saucepans, cook the lentils and quinoa according to package instructions. Drain and cool.
Meanwhile, in a large bowl, whisk the lemon juice and mustard. Gradually whisk in 1/4 cup EVOO; season with salt and pepper. Reserve 1/4 cup of the vinaigrette.
In a large, nonstick skillet, heat the remaining 1 tbsp. EVOO and half the reserved vinaigrette over medium-high. Add the salmon, skin side down. Cover, reduce the heat to medium and cook until the fish flakes apart easily with a fork, about 8 minutes.
Add the quinoa, lentils, onion and 3/4 cup parsley to the bowl with the vinaigrette. Toss to combine; season. Divide among plates and serve the fish on top. Drizzle with remaining vinaigrette and top with remaining parsley.