Boil the eggs until hardness the yolk. Cooling. During this time, chop the tomatoes into slices and salting them, optional peel them. Cut the cooled eggs also circles. Arrange tomatoes and eggs on a plate or platter. Lightly sprinkle olive oil. Prepare the sauce, such as confusion all products for it - mustard, mayonnaise, yogurt and lemon juice - to obtain a homogeneous mixture (I used a blender). Pour a little of the sauce over the salad and the rest serving of table for individual use. Finally, sprinkle the salad with oregano (optional).