Prepare the sauce. In a small bowl, combine the vinegar, sugar, mustard, egg yolk, and vegetable oil. Add 0.5 teaspoon of dill, salt, and pepper to taste.
Grease slices of bread with butter on one side, put lettuce leaves on top. Cut each slice in half.
On each half of the bread put 1 slice of salmon, pour 1 teaspoon of sauce, and put 1 slice of lemon on top. Decorate with dill sprigs.