Step 3: To make the cake
Place a wire mesh strainer over a medium bowl. Add the pastry flour, white flour, sugar, baking powder, baking soda, and salt to the strainer. Tap the strainer against the palm of your hand to sift the ingredients into the bowl. Stir with a wire whisk to distribute the ingredients.
Whisk the oil, maple syrup, soymilk, vanilla, and vinegar in a separate bowl until well blended. Pour into the dry mixture and stir with a whisk until the batter is smooth.