Fry the onion cubes in the hot oil in a large saucepan. Then gradually add the carrots, tomato paste, celery, potatoes, bell pepper, leek and zucchini and fry lightly. Then add the water and simmer until everything is done. If you like, you can puree part of the stew to make it thicker. Then season well with the spices and possibly granular broth.
Instead of potatoes, you can also use soup noodles. The vegetables can of course be selected seasonally.