Step 1Cut the onions, tomatoes, zucchini and potatoes into 1-inch cubes.
Step 2In a large saucepan, cook the onions in the oil over medium heat until tender, about 5 to 8 minutes. Stir in the garlic and cook 1 minute more.
Step 3Add the tomatoes, zucchini and potatoes and salt and pepper to taste. Cover and cook, stirring occasionally, until the potatoes are very tender, 30 minutes. Add a little water if the mixture seems dry.
Step 4When the ciambotta is done, remove it from the heat and stir in the basil. Serve hot or at room temperature.