Mix the flour with the eggs, salt and enough water to make a thick paste. Let the dough rest for approx. 1 hour.
In the meantime, peel the onions and cut into rings. Fry slowly in oil. Meanwhile, grate the cheese.
Stir the dough again, if it is too tough, add a little more water. Then scrape the dough off the board in portions or put it in boiling salted water with a spaetzle slicer, spaetzle machine or spaetzle press. Immediately skim off the surface with a slotted spoon and drain in a colander. Put the spaetzle, onions and cheese in layers in a warmed bowl.