Preheat oven to 350°F and line a regular muffin pan or mini-muffin pan with cupcake liners.
Whisk soy milk and vinegar in a measuring cup and set aside for a few minutes to curdle.
Beat together the soy milk mixture, oil, sugar, vanilla, lemon extract and lemon zest in a large bowl. Sift in the flour, cornstarch, baking powder, baking soda and salt and mix until no big lumps remain.
Fill cupcake liners ⅔rds of the way full and bake for 20-22 minutes or until a toothpick inserted in the center comes out clean.
Transfer to a cooling rack and let them cool completely before frosting.