Prepare the Pan - Set the oven rack to the middle position. Heat to 400ºF (200ºC). Lightly grease the bottom of a cast iron skillet with vegetable or olive oil. Set aside. Alternatively, use a greased parchment paper-lined sheet pan.
Mix the Dry Ingredients - In a large bowl, whisk together the flour, sugar, baking soda, and salt.
Incorporate the Butter - Add the chilled cubes of butter to the bowl. Use fingers or a pastry cutter to break them into smaller pieces. The mixture should resemble coarse cornmeal.
Add the Raisins - Stir in the raisins, then make a well in the center of the flour mixture.
Add the Wet Ingredients - In a medium bowl, whisk together the buttermilk and eggs. Pour the mixture into the well of the flour mixture. Use a spoon to stir until a shaggy dough forms. It will be tacky.
Shape the Dough - Generously flour a work surface. Using floured hands, knead the dough until a ball forms, sprinkling more flour as needed to prevent sticking, about 30 to 60 seconds. Do not overwork!Shape into a 6-inch round ball and transfer to the greased skillet. Cut a shallow "X" into the top, about ½-inch deep and 4 inches long.
Bake - Bake until the center reaches 190ºF (88ºC), the surface is golden brown, and the bottom is hollow when tapped, about 45 to 50 minutes. If you notice the surface getting brown too quickly, loosely cover it with foil.
Cool and Serve - Cool the bread in the pan for 5 minutes, then transfer it to a wire rack. Slice and serve while warm or cool completely.
Notes
Recipe Yield: About an 8-inch loaf
Substituting with Baking Powder: Add 1 tablespoon of baking powder instead of baking soda.
No Buttermilk?: You can try these buttermilk substitutes. However, since the recipe has a large amount, it will taste best with the actual product.
Storing: Cool entirely and tightly wrap in foil—store at room temperature for up to 2 days. Freeze the loaf of slices for up to 3 months.
Reheating: Warm inside the oven at 300 degrees. Alternatively, warm the slices in a toaster.