Preheat oven to 350°F (177°C). Line a 8 inch square baking pan with parchment paper.
Sift flour into a large mixing bowl using a flour sifter or fine mesh strainer. It's important to sift the flour in even if it is labeled "pre-sifted." If you don't sift it in, the cake will be dense and it will also be hard to mix out the flour lumps.
Add in sugar and water. Whisk until you have a thin, smooth batter.
Add in pumpkin puree. Mix with a whisk until the pumpkin is fully incorporated and the batter is uniform in color.
Pour batter into the prepared baking pan. Bake for about 45-50 minutes or until toothpick inserted comes out clean and the cake bounces back if you apply light pressure to the surface. Let cake cool fully before serving. If desired, you can decorate with your favorite frosting after the cake is cooled. I decorated mine with whipped cream frosting and cinnamon. Store any uneaten cake in the fridge.
Notes
If you like fall spices, you can add them to the cake batter. I would add either 1 tsp of cinnamon or 1 tsp of pumpkin pie spice.
How to measure flour: It is very important to properly measure the flour because if you add too much your cake will be too dense and will not rise as much as it should. To properly measure flour, spoon the flour into the measuring cup and then level off with a knife. Do not directly dip the measuring cup into the flour because this results in too much flour. Use this method of measuring whether you are measuring self-rising flour or measuring all purpose flour to make your own self-rising flour.
I used Lily's self-rising flour to make this cake.
Homemade self-rising flour: Whisk together 2 1/4 cup all purpose flour + 3 3/8 teaspoons baking powder + 9/16 teaspoon salt.
Optional Whipped Cream Frosting: Add 1 cup of cold heavy cream and 3 tbsp of sugar to a large mixing bowl. Beat on highest speed until stiff peaks form. Spread over surface of the cake once it is cooled. If desired you can also sprinkle cinnamon on top of the frosting (or add it to the frosting directly when mixing).
Estimated nutrition is for the cake only and does not include the optional frosting.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.