Preheat oven to 450°F.

On a large sheet pan, toss carrots, green beans, onion and lemon with 1 tablespoon evoo, salt, and freshly cracked black pepper. Roast for 15 minutes.

Remove lemon halves, stir veg and move to edges of pan. Place salmon, skin side down, in the center of the sheet pan. Drizzle with 1 tablespoon evoo and sprinkle with salt and pepper. Roast for 15 minutes or until the fish flakes easily.

In a small bowl, squeeze juice from roasted lemons. Whisk in remaining 2 tablespoons evoo, reserved lemon zest, and Dijon mustard. Stir well and season to taste with salt and pepper.

When everything is ready, toss barley with half the dressing and divide among 4 bowls. Top equally with veggies and flaked salmon. Drizzle remaining dressing over top as desired.