Combine tomato soup and baking soda in a bowl; set aside. It will puff a bit.
Beat sugar, butter a large bowl with an electric mixer until smooth.
Add eggs, one at a time, until fully incorporated. Add vanilla and mix until combined.
Mix in the tomato soup mixture.
Sift the flour, cinnamon, nutmeg, all spice and salt into the butter mixture.
Using a spoon, mix until there are no more streaks of flour.
Pour cake batter into prepared baking dish.
Bake in the preheated oven for 45-50 minutes or until a toothpick inserted into the center comes out clean.
While cake is baking, prepare frosting. Add cream cheese and butter to a medium bowl and mix with electric mixer until combined.
Add the powdered sugar and vanilla and mix until smooth.
When cake has finished baking, allow it to cool fully before frosting.
Christina's Notes
Raisins and Nuts: These are classic additions. Soak raisins in a little hot water or even rum for 10 minutes before draining and folding them in to plump them up.
Toss all nuts/raisins with a tablespoon of flour before adding them to the batter; this helps prevent them from sinking to the bottom of the cake.
Dates and Walnuts: This is another popular variation for a richer, fruitier crumb.
Embrace the Spices: The tomato soup cake is fundamentally a spice cake. Use high-quality, fresh spices like cinnamon, nutmeg, cloves, and allspice. You can slightly adjust the amounts to your personal preference; some older recipes are very heavy on cloves.
Consider Molasses: Some vintage versions include a tablespoon or two of molasses. This adds depth, color, and a rich, traditional spice cake flavor that complements the warming spices beautifully.