Boston Brown Bread is dense, sweet, and studded with raisins, It is steamed in a used tomato sauce can, and is possibly the best bread I have ever eaten.
Preheat the oven to 350 degrees. Butter one 28-ounce can (or two 15 1/2-ounce cans). Set a pot of water to a boil.
Whisk together AP and rye flours, cornmeal, baking powder, baking soda, and salt in a large bowl.
Stir in sour cream, molasses, and water. Fold in raisins if using. Pour batter into a prepared can.
Place the can in a deep pot with a tight-fitting lid (foil may also be used) and add enough boiling water to come halfway up the sides of the can. Cover the pot and bake until a cake tester inserted in the center comes out clean, about 1 1/4 hours for 28-ounce bread or about 55 minutes for 15 1/2-ounce loaves of bread.
Remove can from water and let cool slightly on a wire rack.
Turn out bread; shaking can if necessary to loosen. Return to a rack to cool completely. Enjoy!