Place salmon fillets in a foil-lined baking dish or pan, skin sides down. Lightly sprinkle with salt and pepper, then chopped parsley, then chopped leeks. Drizzle with the olive oil then squeeze the juice of 1/2 lemon on top. Bake for 15 to 20 minutes or until fish flakes easily when tested with a fork and leeks are soft and nicely browned.