Preheat the oven to 220°C (425°F). Line a large rimmed baking sheet with parchment or lightly oil it. A hot oven gives the sweet potatoes and salmon enough radiant heat to caramelize and crisp the skin without overcooking the flesh.

Prepare the sweet potatoes: peel (optional) and cut into even 2 cm (3/4 in) wedges or cubes so they roast evenly. Toss the cut sweet potato with 1.5 tbsp (22.5 ml) olive oil, 1/2 tsp salt, 1/4 tsp black pepper and the smoked paprika (if using). Spread in a single layer on one side of the baking sheet with space between pieces so steam escapes and edges caramelize. Cutting evenly and giving space prevents steaming and produces the desirable browned, sweet crust.

Start roasting the sweet potatoes for 12 minutes. Par-roasting the starch first ensures they’ll be tender by the time the salmon finishes but still have crisp edges. After 12 minutes, flip or shake the pan so the other sides can brown.

Meanwhile, pat the salmon dry with paper towels (dry skin crisps better) and season both sides with the remaining 1/2 tsp salt and 1/4 tsp black pepper. Lightly brush the top of each fillet with 1/2 tbsp (7.5 ml) olive oil. Zesting half the lemon over the fillets will add aromatics and bright citrus oils that pair perfectly with salmon.

Combine the herb-garlic butter: in a small bowl, mash together the butter, minced garlic, chopped herbs (reserve a pinch for finishing), and 1 tbsp lemon juice. This compound butter will melt during baking and baste the salmon, adding gloss and an herb-forward flavor. Reserve the remaining lemon for squeezing at the end.

After the sweet potatoes have roasted for roughly 12 minutes and been turned, push them to one side of the pan. Add the salmon fillets skin-side down to the empty area (skin helps hold the fillet together and crisp). Spoon half of the herb-garlic butter over the flesh of each fillet (not the skin). Return the baking sheet to the oven.

At the same time you add the salmon, toss the broccolini with the remaining 1 tbsp olive oil and a pinch of salt and pepper; arrange it alongside the fish and sweet potatoes (or on a second sheet if your pan is crowded). Broccolini cooks quickly and will char slightly at these oven temperatures—exactly what you want for a tender-crisp, slightly smoky bite.

Bake everything for 10–12 minutes, depending on salmon thickness (a 170 g fillet will usually take about 10–11 minutes). Why this timing: the pre-roasted sweet potatoes are already partway tender, the high heat crisps the skin and caramelizes edges, and 10–12 minutes yields salmon that’s medium-rare to medium (internal temp about 52–57°C / 125–135°F). If you prefer well done, add 1–2 minutes but watch closely.

Finish and rest: remove the tray from the oven. Spoon the remaining herb butter over the salmon so it melts into a glossy sauce; squeeze the remaining lemon over the broccolini and sweet potatoes. Let the salmon rest for 2–3 minutes — resting redistributes juices so the fillet stays moist when you cut into it.

Plate: place a portion of roasted sweet potatoes, a nest of broccolini, and the salmon fillet on each plate. Sprinkle the reserved chopped herbs and a light pinch of flaky sea salt over the fish for sparkle. Serve immediately with extra lemon wedges on the side.