1. Chop a leek radially into thin rings. Rinse out grit if necessary. Chop a large red onion into rings. Sweat the leek and onion in oil in a covered pan until they just start to soften.
2. In a bowl, combine three tablespoons of olive oil with the juice of two lemons, a handful of chopped parsley and half that amount of chopped dill. Season.
3. Place two large salmon fillets into a baking dish and cover with warm leek and onion mixture. Pour over the herbed oil and lemon mixture. Cover dish with foil. Bake twenty minutes depending on size of fish. Salmon cooks quickly, staying moist.
4. Serve with asparagus drizzled with lemon butter: boil and remove asparagus from pan, drain most cooking water, add the juice of two lemons and a pat of butter, reduce, pour over asparagus and add cracked black pepper.