Preheat oven to 425°F (220°C). Set an oven rack in the center position. Preheating to a high temperature lets the sweet potatoes caramelize quickly and allows the salmon crust to brown without overcooking the flesh.

Prepare the sweet potatoes: toss the 1/2" cubes with 2 tbsp olive oil, 1 tsp kosher salt and 1/2 tsp black pepper on a rimmed baking sheet so pieces are in a single layer. Why: a single layer ensures even roasting and caramelization; olive oil promotes browning and crisps the edges.

Roast the sweet potatoes for 20 minutes, then use a spatula to flip/turn them so the exposed sides brown evenly. Return to the oven while you prepare the salmon. Why: turning halfway encourages uniform caramelization and prevents burning on the high heat.

Make the herb-breadcrumb topping: in a bowl combine 3/4 cup breadcrumbs, chopped parsley, chopped dill, the zest of the lemon, 1 tbsp olive oil, 1/4 tsp kosher salt and 1/4 tsp black pepper. Toss to combine and press a small handful in your hand — it should hold together slightly. Why: the small amount of oil transfers flavor and helps the crumbs adhere to the salmon; lemon zest brightens the herbs so the crust tastes fresh, not heavy.

Pat the salmon fillets dry with paper towels (moisture prevents browning). Season both sides lightly with the remaining 1/2 tsp kosher salt and 1/2 tsp pepper. Brush the top (skin-side up if using skin-on) with about 1 tsp lemon juice and a light brush of olive oil. Why: drying ensures the crust sticks and browns; a little acid (lemon) lifts the fish flavor without 'cooking' it as vinegar or too much citrus might.

Press the herb-breadcrumb mixture onto the top of each fillet, covering the surface in a compact layer (about 2–3 tbsp topping per fillet). Place the fillets on a separate lightly oiled baking sheet (or line the sweet potato sheet with foil if there’s space). Why: pressing the topping ensures contact so it crisps rather than falls off during baking.

When the sweet potatoes have roasted for ~20 minutes and are starting to caramelize, place the salmon tray in the oven as well. Bake both trays at 425°F: salmon 10–12 minutes for 1" thick fillets (internal temp ~125–130°F/52–54°C for medium-rare to medium), and continue roasting the sweet potatoes another 5–10 minutes until fork-tender and golden. Why: cooking both at the same temp saves time; high heat cooks the salmon quickly so it remains moist and lets the crust brown.

Optional finishing step for a crisper crust: switch the oven to broil (high) for 1–2 minutes, watching closely, to toast the breadcrumb topping. Why: broiling quickly browns and crisps the crust without overcooking the salmon interior. Do not walk away — breadcrumbs burn fast under a broiler.

While the salmon finishes, steam the broccoli: bring an inch of water to a simmer in a medium pot with a steamer basket. Add the broccoli florets, cover, and steam for 4–6 minutes until bright green and tender‑crisp. Immediately transfer to a bowl and toss with 1 tbsp olive oil (or a pat of butter) and the minced garlic (if using) and 1–2 tsp lemon juice; season to taste with salt and pepper. Why: steaming briefly preserves the broccoli’s vibrant color and snap; finishing with acid and oil balances the plate.

Rest the salmon 2 minutes after it comes out of the oven—this lets residual heat finish cooking gently and the juices redistribute. Plate: spoon roasted sweet potatoes, arrange a salmon fillet (herb crust up), and add a mound of steamed broccoli. Garnish with lemon wedges and a scattering of extra chopped parsley or dill. Why: resting avoids dry fish and gives a polished presentation.

Serve immediately so the crust retains its crunch and the salmon remains tender. Leftovers: store cooled components separately in airtight containers for up to 2 days (salmon texture will change when reheated).