Slow-Roasted Salmon with Potato Salad and Dill Mustard Mayo

Preheat the oven to 120C (100C fan/gas 1/2). Scatter the lemon slices, thyme sprigs, and reserved dill stalks in a large shallow roasting tin. Season the salmon generously with salt and black pepper, then rub with half of the olive oil. Place the salmon skin-side up on the lemon and herbs and roast for 45-50 minutes, or until the fish is just firm and the skin lifts away easily. If using a thermometer, the thickest part should reach about 55C. Let the salmon cool slightly in the tin.

While the salmon roasts, put the potatoes in a large pan of cold salted water. Bring to a boil, then reduce to a simmer and cook for 10-15 minutes until just tender. Drain well.

Whisk 1 tbsp mustard, the lemon juice, and the remaining olive oil in a large bowl. Season lightly with salt and black pepper. Add the hot potatoes and toss gently so they absorb the dressing. Set aside and serve warm, or chill for later.

To make the dill mustard mayo, stir together the mayonnaise, the remaining 1 tbsp mustard, and the chopped dill leaves in a small bowl. Keep chilled until ready to serve.

Transfer the salmon to a serving platter if you like, or serve it straight from the roasting tin. Peel off and discard the skin, then gently scrape away the grey layer if preferred, revealing the pink flesh underneath.