Preheat oven to 425°F / 220°C.

1. Mix together the flour, sugar, salt, and baking soda into a large mixing bowl.
2. Using a pastry cutter or 2 knives, work butter into flour mixture until it resembles coarse meal, then stir in raisins.
3. Make a well in the center of the flour mixture. Add beaten egg and buttermilk to well and mix in with a wooden spoon until dough is too stiff to stir.
4. Dust hands with a little flour, then gently knead dough in the bowl just long enough to form a rough ball. Transfer dough to a lightly floured surface and shape into a round loaf.
5. Bake in a large, lightly greased cast-iron skillet or a baking sheet. Using a serrated knife, score top of dough about 0.5" deep in an X shape. Bake until bread is golden and bottom sounds hollow when tapped with a knife, about 40 minutes.
6. Transfer bread to a rack to let cool briefly.