Heat the oven to 400 degrees F. Line a baking sheet with parchment paper.
Place the salmon fillets and asparagus on the sheet. Drizzle with 1 tablespoon olive oil, half the lemon juice, half the garlic, salt, and pepper. Toss the asparagus to coat.
Bake for 12 to 15 minutes until the salmon flakes easily and the asparagus is tender.
While the salmon bakes, bring the vegetable broth to a boil in a saucepan. Stir in the couscous, cover, and remove from heat. Let it sit for 5 minutes.
Fluff the couscous with a fork. Stir in the cherry tomatoes, remaining olive oil, remaining garlic, lemon zest, remaining lemon juice, salt, pepper, and parsley.
Divide the couscous among four plates and top each with one salmon fillet and some asparagus.