Preheat oven to 425 degrees F. Line a rimmed baking sheet with foil and lightly spray with cooking spray.
In a small bowl, whisk together olive oil, lemon zest, lemon juice, garlic, salt and pepper. Reserve ¼ cup of the mixture by placing it in another small bowl or measuring cup.
Arrange the salmon pieces down the center of the baking sheet and drizzle/brush with the lemon juice mixture, saving the reserved ¼ cup for the asparagus. Place salmon in the preheated oven and bake for 5 minutes.
Remove the pan from the oven and add the asparagus along the sides of the pan. Drizzle asparagus with the reserved ¼ cup lemon juice mixture and toss gently to coat.
Return the pan to the oven and continue baking for about 10 minutes, until salmon is cooked through. If desired, turn on the broiler during the last 2-3 minutes of baking to help the salmon and asparagus brown on top. Season with more salt and/or pepper, to taste, as needed.
While the salmon and asparagus cook, prepare the couscous according to package directions. Fluff with a fork. Top couscous with a squeeze of lemon juice, sliced almonds and a sprinkle of parsley. Serve alongside salmon and asparagus, with additional lemon slices and parsley as desired.