01 - Preheat oven to 400°F. Line a baking sheet with parchment paper or lightly grease it.
02 - In a large bowl, whisk together whole wheat flour, all-purpose flour, baking soda, salt, and sugar.
03 - Add raisins and toss to coat them in the flour mixture.
04 - In a separate bowl, combine buttermilk and melted butter.
05 - Make a well in the center of the dry ingredients and pour in the wet mixture. Stir with a wooden spoon until a shaggy dough forms.
06 - Turn the dough onto a lightly floured surface. Knead gently just until it comes together (about 30 seconds); do not overwork.
07 - Shape into a round loaf (about 7 inches in diameter) and place on the prepared baking sheet.
08 - Using a sharp knife, cut a deep X across the top of the loaf.
09 - Brush the top with a little extra melted butter. Bake for 35–40 minutes, or until golden brown and the loaf sounds hollow when tapped on the bottom.
10 - Cool on a wire rack for at least 30 minutes before slicing.