Tear white bread cubes coarsely. Peel onion and garlic and roughly chop. Rinse cucumber and bell peppers. Finely chop half of each and reserve. Cut remaining cucumber and bell peppers into chunks. Combine cucumber and bell pepper chunks, onion, garlic, peeled tomatoes, bread, cumin and vinegar in a blender. Puree and gradually blend in the oil. Season with salt and pepper. Stir finely diced vegetables into the soup and refrigerate. Garnish with parsley.
Serve with toasted garlic bread, if desired.