Preheat oven to 400°F and line a large sheet pan with parchment paper or aluminum foil.
In a small bowl, whisk together brown sugar, soy sauce, Dijon mustard, and minced garlic to make the glaze.
Toss halved potatoes with 2 tablespoons olive oil, ½ teaspoon salt, and ¼ teaspoon pepper. Spread on one side of the sheet pan and roast for 10 minutes.
After 10 minutes, remove pan from oven. Add asparagus tossed with remaining 1 tablespoon olive oil and remaining salt and pepper to the other side of the pan.
Place salmon fillets on top of the asparagus and brush generously with the brown sugar glaze, using all of it.
Return to oven and bake for 10-12 minutes until salmon flakes easily with a fork and reaches an internal temperature of 145°F.
Serve immediately with lemon wedges and garnish with fresh dill if desired.