Heat oven to 350°F/175°C. Spray a 9x13 baking pan with vegetable spray
In a medium-size bowl combine the water, vinegar, oil, sugar, and pumpkin. Stir to combine. Set aside.
In a separate bowl, stir together the flour, cornstarch, salt, baking soda, and spices. Whisk until well combined. Create a well in the middle of the flour ingredients.
Pour the pumpkin mixture into the bowl with the flour mixture. Use a whisk to stir until well-combined.
Pour the batter into the prepared cake pan and bake for about 35 to 40 minutes. Insert a tester in the center. If it comes out clean or mostly clean (with only a few crumbs), the cake is done. If not, return it to the oven and bake for another 5 minutes or so.
When the cake is done, remove it from the oven and allow it to cool completely before adding the Vegan Cream Cheese Frosting.
Notes
For flour, you can use whole wheat pastry flour, gluten-free baking flour, or all-purpose flour.The nutritional estimate is based on the cake without the cream cheese frosting.