Preheat the oven to 180°C.
Run flour and powdered sugar through a sieve into a big bowl. Add baking powder, lemon zest and salt and mix well. In the middle of the flour add canola oil, soy milk and vanilla. Divide margarine into flakes and sprinkle over the flour. Kneat everything to an even dough.
Roll out the dough to a thickness of about 1cm. Cut out the desired shapes and put on a baking sheet covered with baking paper.
Bake the biscuits for 10 minutes. Then let cool down.
Mix lemon juice and powdered sugar in a bowl to an icing. Add icing and some more powdered sugar on top of the warm biscuits.