Clean potatoes and onion, cut the first cubes and chop the second.

Brown the onion in a saucepan with a little oil, then add the potatoes too.
Briefly flavor, then cover with the hot broth and start cooking: bring to the boil, then allow 20 minutes for cooking.

In the meantime, rinse the quinoa under running water, put it in a saucepan with twice its weight in water and cook for 10-12 minutes starting from the boil.
Also prepare the lentils (if you have not pre-cooked them, simply boil them for about 40 minutes).
Then add quinoa and lentils to the pot with the potatoes, stir, season with salt and continue cooking for another 10 minutes.

The quinoa and lentil soup is ready, serve it immediately.