- Preheat the oven to 375°. Butter an 8-by-5-inch metal loaf pan.
- In a large bowl, whisk both flours with the baking soda and salt. In a small bowl, whisk the buttermilk with the egg; stir into the dry ingredients with a wooden spoon until a rough dough forms.
- Transfer the dough to a lightly floured work surface and knead until smooth. Form the dough into a loaf and put it in the prepared pan. Bake for about 50 minutes, until the bread has risen about 1/2 inch above the rim of the pan. Once unmolded, the loaf should sound hollow when tapped on the bottom. Let cool to warm or room temperature, then slice and serve.