Preheat oven to 350 degrees. Coat a bundt or tube pan with cooking spray, such as Pam, and set aside.
In a medium sized bowl, pour in the tomato soup and add the baking soda. Whisk gently to combine. Set aside. (The baking soda will foam when it reacts with the acid in the soup. Make sure your bowl is big enough to hold it!)
In a large bowl, use a hand-held mixer to blend the butter and sugar until light and fluffy.
Add the egg and blend to incorporate.
Next, pour in the tomato soup and blend into the butter and sugar mixture.
Add the flour, pumpkin spice, baking powder, and salt. Mix until just incorporated. Do not over mix the batter.
Add the raisins and use a rubber spatula to fold them in.
Pour the cake batter into the prepared bundt or tube pan. Tap the cake pan firmly onto your counter top or a cutting board to ensure the batter has gotten into the crooks and crannies of your bundt pan. This action will also help to eliminate some of the air bubbles.
Bake for 50 minutes, or until a wooden toothpick inserted into the center of the cake, comes out clean.
Remove from oven and allow cake to cool in the pan for 10 minutes. Then turn the cake out onto a wire cooling rack to finish cooling.
To serve, dust with some confectioner's sugar - optional.