1 cup milk
2 tablespoons distilled white vinegar
2 cups all-purpose flour
1 tablespoon white sugar
1/2 teaspoon baking soda
1/2 teaspoon salt
Stir the milk and vinegar together, and set aside until curdled, about 10 minutes.
Preheat oven to 400 degrees F. Grease a baking sheet. In a bowl, mix together the flour, sugar, baking soda, and salt.
Gradually stir the soured milk into the flour mixture until the dough just comes together, and turn the dough out onto a well-floured surface. Knead a few times, and shape into a round. Place the dough onto the prepared baking sheet. With a sharp knife, cut an X shape into the top of the dough to release steam and help the bread keep its round shape.
Bake in the preheated oven until golden brown, about 45 minutes.