Soda bread has been an Irish household staple since baking soda became commercially available in the early 19th century. It uses just four ingredients that most people kept on hand: flour, salt, baking soda, and buttermilk (raisins and caraway seeds are an American addition). A real soda bread is a simple loaf with a beautifully browned, craggy crust and a nice chew, best eaten liberally smeared with salty Irish butter.
1 lb. (3-1/2 cups) unbleached all-purpose flour; more as needed
3/4 tsp. baking soda
1/2 tsp. table salt
1-1/2 to 1-3/4 cups buttermilk
Position a rack in the center of the oven and cook’s tip heat the oven to 450°F. Lightly flour a large rimmed baking sheet.
Sift all of the dry ingredients into a large, wide mixing bowl. Make a well in the center and pour in 1-1/2 cups of the buttermilk. Stir with one hand, fingers apart, moving in circles to incorporate the buttermilk into the dry ingredients. If necessary, add more buttermilk 1 Tbs. at a time until the dough just barely comes together. (The absorption rate varies depending on the brand of flour.) The dough should be soft—don’t overwork it.
Turn the dough out onto a well-floured surface and pat into a round about 6-3/4 inches in diameter and 1-1/2 inches high in the center. Invert the round so the floured side is on top. With a thin, sharp knife, score a cross on the dough about 1/4 inch deep and extending fully from one side to the other.
Transfer the dough to the prepared baking sheet and bake for 15 minutes. Lower the oven temperature to 400°F and bake until the bread is browned and sounds hollow when tapped on the bottom, another 20 to 30 minutes.
Cool to room temperature on a rack, about 2 hours, before slicing and serving.