Pro Tips: The reaction between buttermilk and baking soda starts immediately – work quickly and get the bread into the oven as soon as possible. Use fresh baking soda and real buttermilk for the best rise. The dough should be slightly sticky; resist adding too much extra flour. For a crustier loaf, preheat a cast-iron skillet or baking stone in the oven. The loaf is done when it sounds hollow when tapped on the bottom.