Preheat your oven to 350°F (175°C). Grease a 9×5-inch loaf pan or two 1-pound coffee cans with cooking spray or a thin coating of oil. Set aside.

In a large bowl, whisk together the whole wheat flour, cornmeal, rye flour, baking soda, salt, cinnamon, and allspice until well combined.

Add the molasses and buttermilk to the bowl. Stir gently with a wooden spoon or spatula until just combined — don’t overmix, as that can make the bread tough.

Gently fold in the raisins until they are evenly distributed throughout the batter.

Pour the batter into the prepared loaf pan or divide evenly between the two coffee cans, leaving about an inch of space at the top to allow for expansion. Cover tightly with aluminum foil to prevent water from seeping in during baking.

Place the loaf pan or cans inside a large roasting pan. Carefully pour boiling water into the roasting pan until it reaches halfway up the sides of the loaf pan or coffee cans.

Bake in the preheated oven for 60–70 minutes, or until a toothpick inserted into the center comes out clean.

Carefully remove the loaf pan or cans from the water bath. Let the bread cool completely on a wire rack before slicing. Serve thick slices with butter, baked beans, or a hearty winter stew.