In a large mixing bowl, dissolve yeast in warm water. Add 1 tablespoon sugar; let stand for 5 minutes.
Beat in the buttermilk, butter, salt, baking soda, 1 cup flour and remaining sugar until smooth.
Stir in raisins and enough remaining flour to form a soft dough.
Turn onto a floured surface; knead until smooth and elastic, about 6-8 minutes.
Place in a greased bowl, turning once to grease top.
Cover and let rise in a warm place until doubled, about 40 minutes.
Punch dough down. Turn onto a lightly floured surface; knead for 2 minutes.
Shape into a round loaf. Place on a greased baking sheet.
With a sharp knife, cut a ¼-in.-deep cross on top of loaf.
Cover and let rise until doubled, about 30 minutes.
Bake at 350° for 30-35 minutes or until golden brown.
Remove from pan to cool on a wire rack.
