Preheat the oven to 375 degrees F.

Grease or line your pan with parchment paper. (You can skip this step if you're using a well-seasoned cast iron pan.)

In a bowl, mix together both kinds of flour, the baking soda, the salt, and the sugar.

Gradually stir in the buttermilk until the mixture becomes too stiff to stir.

Turn out the mixture onto a clean, lightly floured countertop and knead it gently just until the dough comes together.

Add the raisins and knead again, just until they are folded in. Be careful not to overwork the dough. It should remain somewhat wet and sticky.

Transfer the dough to your prepared pan and score a cross into the top with a very sharp knife.

Bake for 25-35 minutes or until a cake tester comes out clean. The loaf should sound hollow when tapped.