Cream the margarine and sugar until light and fluffy.
Add the yogurt, egg whites, grated lemon rind and vanilla and mix until combined. Gradually add all the other ingredients except for the icing sugar.
Cover the mixture and refrigerate for 1 to 3 hours.
Preheat the oven to 190 degrees Celsius.
With lightly-floured hands, shape the mixture into small balls and place on the baking tray. Dip the bottom of a glass into the icing sugar and lightly press it down onto each of the balls to form cookies.
Bake for approximately 10-12 minutes or until the edges turn golden brown. Leave to cool for 2 minutes for easy removal.