For the mayonnaise, put the egg yolks, mustard, salt, sugar and vinegar (lemon juice) in a mixing bowl and beat with a whisk until you have a thick mixture. Beat the oil under it. With this preparation it is not necessary to add the oil drop by drop, it is added in amounts of 1-2 tablespoon. The spices added to the egg yolk prevent coagulation.
Thicken the crabs and the sliced eggs (add a little salt if you like) with the mayonnaise. Arrange the lettuce on lettuce leaves and garnish with sliced tomatoes.