Peel the asparagus in the lower third and cook in the bouillon for 12-15 minutes. Drain and save some cooking water.
For the sauce, mix the egg yolks and mustard, slowly add the oil and stir into the mayonnaise. Add capers and season with salt and pepper. Drain the tuna, chop and stir into the mayonnaise. Add some bouillon and mix. Nap the lukewarm asparagus spears with the sauce.