Peel the asparagus and cook in salted water with 2 tablespoons of butter, halved lemon, orange and a pinch of sugar.
In the meantime, heat the butter and sauté the onion until translucent. Dice the rolls and eggs. Cut off the cress. Skin, core and finely chop tomatoes. Toast the bun cubes in onion butter. Briefly heat the egg, cress and tomatoes. Season to taste with salt, pepper, lemon juice and a pinch of sugar.
Arrange the asparagus, cover with the egg sauce and serve immediately.