This vegan soup is the definition of effortless Italian comfort food! Stale or toasted bread, fragrant basil, and juicy-sweet San Marzano tomatoes simmer together until you have a savory custard the whole family will love. Throw together an simple salad while it simmers and you have a weeknight dinner on your table in just about 30 minutes!
Prepare the ciabatta. Slice the ciabatta in half lengthwise, then use your hands to pull off and tear the center into small pieces (or you can cut it into 1-inch cubes). If you’re working with very dry stale bread, skip to the next step. Otherwise, spread onto a sheet pan and drizzle with olive oil. Toss to coat, then broil on high until golden, about 2 minutes. Set aside.
Sauté the vegetables. In a medium saucepan, heat 2 tablespoons olive oil over medium heat until shimmering. Add the red pepper flakes and lower the heat to medium-low. Add the garlic and onions and cook over medium-low heat, stirring occasionally, until the mixture is lightly golden (do not let it burn or turn dark brown), 10 to 15 minutes.
Meanwhile, make large rustic tomato chunks. When the onions are lightly golden, use your hands dig out the tomatoes from the can and burst them into large chunks over the pan. Pour in the juices from the can, then add the basil sprigs. Turn the heat to high to bring to a simmer.
Simmer. When the soup is simmering, stir in the bread and 2 cups of broth. Lower the heat to medium-low and simmer, stirring occasionally and adding more broth if needed, until the bread is very soft and you have a thick porridge-like consistency—about 20 to 30 minutes.
Finish and serve. Taste and season with salt and pepper to your liking. Remove the basil sprigs, then ladle the soup into bowls and drizzle with a generous amount of olive oil. Garnish with chopped basil and torn bread and serve.
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Notes
If you're working with a rustic loaf of bread with tougher crusts than ciabatta, discard the crust and only use the center.
The bread needs to be rather dry and hard to slowly absorb the broth without falling apart, but if you're working with stale bread feel free to skip the toasting step.