Clean and chop the cabbage, onion, carrot, and celery into bite-sized pieces.
Heat olive oil in a pot and sauté the prepared vegetables.
When the vegetables are partially cooked, add water and bring to a boil.
Chop the tomato and add it to the pot, letting it simmer together.
Season with salt and pepper to taste.
Crack one egg into the soup, stir gently, and cook until the egg is set.
Cut the bread into bite-sized pieces and serve it on the side.