Bring a medium saucepan of well-salted water to a boil. Reduce heat to a simmer. Season fish with salt and pepper and add to water. Cook at a low simmer until fish is cooked through, 5 to 7 minutes. Flake into pieces.
Spread goat cheese on toasted baguette. Top one slice of the baguette with salmon, asparagus, and juice of the lemon wedge. Top with second slice.