Measure flours by lightly spooning into measuring cups and levelling with a knife. As you may know, scooping flour will cause you to use too much.
Whisk or sift together flours, sugar, salt, baking powder and baking soda.
Add wet mixture to dry mixture and stir just until combined.
Add raisins, stirring until the dough pulls together in a shaggy mass . The original recipe suggests a wooden spoon for this.
Split dough in half. With each half, turn out onto a floured surface and knead for 1 minute. Expect the dough to be sticky and wet. Form into a 6-inch round loaf and place on a baking tray sprinkled with cornmeal.
Make 3, 1/4 inch deep, diagonal cuts across each loaf.
Bake at 400°F for 20 minutes, then for 15 minutes more at 375°F These loaves will look browned before they are actually finished, so test for doneness by knocking on the bottom of the loaf. It will sound hollow when finished.
Let stand about 15 minutes before slicing to serve.