Preheat the oven to 350 degrees F. Spray a loaf pan with nonstick cooking spray.
Puree the tomatoes in a blender and measure out 2 cups for the cake. Reserve any remaining juice for the glaze.
In the bowl of a stand mixer, cream the brown sugar and butter together until light and fluffy. Beat in the eggs one at a time, and then mix in the 2 cups tomato puree. Sift together the flour, baking soda, cinnamon and salt in a bowl. Add the dry ingredients to the tomato-butter mixture and mix to combine.
Pour the batter into the prepared pan and bake until a toothpick inserted in the center comes out clean, 45 to 50 minutes. Let cool slightly, and then remove from the pan and transfer to a rack to cool completely.
To make the tomato glaze, mix together the confectioners' sugar and 2 tablespoons of the reserved tomato juice until the mixture reaches a glaze-like consistency. Drizzle over the top of the cake.