Preheat the oven to 200°C (top and bottom heat). Place a piece of aluminum foil on the baking sheet and brush it with a little oil.

Thoroughly wash the asparagus, gently pat dry, and trim off the woody ends. Lay the asparagus spears side by side on a baking sheet, then drizzle with about 1 teaspoon of oil, and season with salt and pepper. Toss or brush to coat evenly.

Rinse the salmon under cold water and pat dry. Place it skin-side down (if it has skin) on the prepared foil. Rub the top with about 1 teaspoon of salt and season with additional salt and pepper to taste.

Cut the lemon in half. Squeeze one half over the asparagus and salmon, and place the other half on the baking sheet. Roast in the oven for 12 to 15 minutes, or until the asparagus is tender and the salmon is cooked through.

Meanwhile, cut the cooked potatoes in half or thirds. Heat the remaining oil in a large skillet over medium-high heat and sauté the potatoes for about 3 to 5 minutes. Lightly salt them and turn once the bottoms are golden brown, then continue cooking for another 3 to 4 minutes over medium heat until the potatoes are crispy all around.

Use two forks to flake the salmon into bite-sized pieces. Divide the potatoes, salmon, and asparagus between two plates, and drizzle with the juice from the warm lemon halves.