Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Rinse salmon, dab dry and place in an ovenproof dish. Wash lemon hot, dry, finely grate the peel. Cut the fruit in half and squeeze.
Sprinkle salmon with lemon juice. Season with salt and pepper, sprinkle with lemon peel. Bake in a hot oven on a rack above the asparagus for about 15 minutes.
For the tarragon sauce, knead 2 tablespoons of butter with flour and chill. Wash the tarragon, shake dry and chop coarsely. Lightly brown 2 tablespoons of butter. Deglaze with 1⁄4 l water and orange juice. Stir in the stock, bring to the boil and boil down by about 1⁄3. Add cream, bring to the boil. Season with orange peel, salt, pepper and honey. Stir in flour butter bit by bit, simmer sauce for about 5 minutes. Stir in tarragon, season again.