Mix the sugar, salt and lemon peel together in a small bowl.
Lay the salmon in a shallow dish and sprinkle the marinade over.
Leave to marinate for one hour and then rinse off under cold running water.
Divide the fish into four portions.
Put the olive oil in a large frying pan and heat to 45C/113F using a kitchen thermometer to check. If you don't have a thermometer, place the pan onto the heat, then dip a spoon in after 30 seconds. Feel the spoon to check the heat of the oil – it needs to be just warm. Keep the oil on the heat and keep checking every 30 seconds until the oil feels warm. Add the salmon to the pan, turn off the heat and leave the salmon for about 15-20 minutes.
Set aside to cool, then transfer to a plate and leave in the fridge until ready to serve.
For the mustard sauce, mix all ingredients together in a small bowl and chill until required.
For the cucumber salad, peel the cucumber and slice it into 1cm/½in cubes.
Mix the cucumber with the vinegar, salt, olive oil and mustard in a bowl and set aside to marinate.
Add the dill just before serving.
For the rye croûtons, drizzle the bread slices with olive oil and sprinkle with salt.
Heat a frying pan and fry the rye bread until browned all over. Remove from the heat and transfer to a plate to cool slightly before breaking up into rustic croûtons. Sprinkle with the chopped dill.
Sprinkle the chopped dill over the salmon and serve it with the rye croûtons, mustard sauce, cucumber salad and mixed micro leaves to garnish.