Preheat the oven to 400 degrees F, and line a rimmed baking sheet with parchment paper. Place the 4 salmon fillets on the parchment and salt and pepper liberally.
Once the oven is preheated, bake the salmon for 8-9 minutes until just barely cooked through.
Meanwhile, trim the ends off the asparagus and cut into 1 1/2-inch sections. Cut the watercress off the roots and slice the avocado, cucumber and beets.
Pour the lemon juice, olive oil, ginger, Dijon mustard, and minced garlic into a jar. Season with 1 teaspoon salt and 1/2 teaspoon pepper. Screw the lid on the jar and shake until thoroughly mixed.
Arrange the watercress, asparagus, cucumber slices, beet slices, and avocado in four salad bowls. Once the salmon comes out of the oven, place one piece over the top of each bowl, then drizzle with the lemon-ginger dressing!