Wash the asparagus, peel the lower third and cut off the ends. Cook in salted water for about 7 minutes, then quench. Halve the tomatoes, core them and cut into fine cubes.
Whip the white wine vinegar with balsamic vinegar, salt and lemon pepper while slowly pouring in the oil. Stir in the diced tomatoes.
Heat the butter in a non-stick pan, wrap each asparagus in a slice of ham and fry until golden brown while turning.
Arrange on plates and spoon over the vinaigrette. Scatter marjoram on top.