Drain the soaked lentils in a sieve and pour them into a soup pot. Add one and a half liters of water. Peel one onion, halve it and cut it into slices. Rinse and clean the celery stalk and cut it into pieces. Stir into the lentils with the onion and a little salt and pepper, do at a moderate temperature for 30 minutes.
In the meantime, peel the second onion and cut it into small cubes. Heat the olive oil in the frying pan. Sauté the onion and garlic until translucent. Add the tomatoes with the juice, mash them with a wooden spoon and let them bubble up. Rinse the parsley, shake dry well, chop the leaves and stir into the tomatoes. Cover the lid and simmer on low heat for ten minutes.
Cook the macaroni in lightly salted water for ten minutes until al dente and drain. Stir into the lentils and cook for another one or two minutes. Stir in the vegetables from the frying pan, diluting the soup with a little hot water if desired. Gently make the soup for another five minutes, season strongly with salt and freshly ground pepper and bring to the table with the cheese for sprinkling.