Preheat the Oven: Preheat the oven to 200°C (180°C fan) and line a large baking tray with non-stick baking paper.
Roast the Potatoes: Place the halved potatoes on the prepared tray. Drizzle with 2 tablespoons of olive oil, season with salt and pepper and toss to coat. Roast for 10 minutes to give the potatoes a head start.
Add the Salmon: Pat the salmon dry with kitchen paper and place it in the centre of the tray with the potatoes arranged around it. Drizzle the salmon with 1 tablespoon of olive oil and season with salt and pepper. Return the tray to the oven for 5 minutes.
Add the Asparagus: Arrange the asparagus around the salmon and potatoes. Drizzle with the remaining tablespoon of olive oil and season lightly with salt and pepper. Return the tray to the oven for 10–15 minutes, until the potatoes are golden and tender and the salmon is cooked through.
Make the Honey Garlic Sauce: While the salmon finishes cooking, melt the butter and honey together in a small saucepan over medium-low heat. Add the garlic and cook for 1–2 minutes until fragrant, without letting it brown. Remove from the heat, then stir in the juice of half the lemon and the chopped parsley.
Finish and Serve: Remove the tray from the oven and spoon the warm honey garlic butter generously over the salmon. Slice the remaining lemon into wedges and serve alongside.