Roast the potatoes: Preheat oven to 400°F (205°C). In a sheet pan, or a large, shallow roasting pan (not glass, as it might break in an oven that hot) toss the potatoes with olive oil and sprinkle all over with salt.

Place the potatoes cut side down in the roasting pan and cook for 10-12 minutes, until the potatoes begin to brown on the bottom.

Turn the potatoes over and roast another 10 minutes until browned on top. Remove the roasting pan from the oven.

Toss asparagus with dill, zest, garlic, salt, olive oil, and mix with potatoes: In a medium bowl, toss the asparagus with the chopped dill, lemon zest, garlic, about 1/2 teaspoon of salt and a little olive oil. Add the asparagus mixture to the potatoes and stir to combine.

Make room for salmon fillets in the pan, and roast: Push the vegetables to the side of the dish to make room for the salmon. If you are using fillets, put them skin side down. Salt the salmon well and return the baking dish to the oven.

Roast the salmon and asparagus for 10 minutes, or until the fish is just cooked through.

If you want, remove the skin and center bones (if you are using steaks), and arrange on individual plates before serving. Garnish with fresh dill and lemon wedges.