Wash and dry all produce. Preheat oven to 450 degrees. Halve, peel, and finely chop onion. Zest lemon until you have 1/2 tsp zest, then halve crosswise. Slice one half into thin rounds. Trim and discard bottom inch from asparagus stalks. Mince chives. Mince tarragon until you have 1 TBSP.

Heat a drizzle of olive oil in a small pot over medium heat. Add onion and cook, tossing, until softened, 4-5 minutes. Add 1 cup water and a large pinch of salt, then bring to a boil. Once boiling, add couscous. Cover, remove from heat, and let stand until rest of meal is ready.

Tear off two sheets of aluminum foil, each large enough to wrap a salmon fillet. Lay a salmon fillet on each. Season all over with salt and pepper. Place two lemon rounds on top of each, then sprinkle with a small amount of chives (save some chives for the sauce). Fold over aluminum foil and crimp edges to seal into two packets.

Place packets with salmon on one side of a baking sheet. Toss asparagus with a drizzle of olive oil and a pinch of salt and pepper on other side of sheet. Roast in oven until salmon is cooked through and asparagus is tender, 10-12 minutes. TIP: Be careful when unwrapping the cooked salmon—it may release steam.

In a small bowl, combine tarragon, remaining chives, half the zest, and a large drizzle of olive oil. Season with salt, pepper, and a squeeze or two of lemon (to taste).

Fluff couscous with a fork and season with salt, pepper, and a pinch of remaining zest. Divide between plates along with salmon and asparagus. Drizzle with sauce and a squeeze of lemon. TIP: For a pretty presentation, leave the lemon rounds on the salmon— just remove them before eating.