In a saucepan, whisk together water and 1/3 cup flour, stirring so there are no lumps. Whip in silken tofu, which has been blended until smooth and creamy. Stir constantly over low heat until thickened. Cool completely.
To the cooled mixture, add sugar, salt, vanilla. Beat well.
In another bowl, mix together cocoa powder and oil. Add to the other ingredients and stir well. Separately, stir together remaining flour and baking powder. Add this to the mixture above and stir until there are no lumps.
Using a safe cooking spray, coat a 9x13 pan; pour in batter and bake for 35 minutes or until a knife inserted in the middle comes out clean.
Adapted from Tofu Cookery by Louise Hagler.
Corn Substitutions: Corn is a common ingredient in products. Starch, modified food starch, dextrin and maltodextrin can be from corn. Consult with your physician to find out which corn derivatives you need to avoid. Many corn-free options are available in the US. Find out more about corn substitutions.
Gluten: Gluten is a protein found in specific grains (wheat, spelt, kamut, barley, rye). Other grains are naturally gluten-free but may have cross-contact with gluten-containing grains. Look for certified gluten-free products if you need to avoid gluten. Find out more about wheat and gluten substitutions.