Serves 4 to 6 * 1 large onion, diced * 2 medium green peppers, diced * 3 tablespoons olive oil * 1 1/2 cups boiling water * 2 1/2 cups tomato purée * freshly ground pepper, to taste * 1 tablespoon soy sauce * 1 1/2 tablespoons mustard * 1 tablespoon sugar...