2 1/2 cups all-purpose flour
1/4 teaspoon baking soda
1 teaspoon baking powder
1 cup white sugar
1 teaspoon vanilla extract
1 teaspoon lemon zest
16 shortbread cookie sheets
Preheat oven to 350 degrees F (175 degrees C). Line cookie sheets with waxed paper.
Brown sugar and baking soda in a large bowl. Beat in sugar, vanilla extract and lemon zest. Combine flour and baking soda; stir into brown sugar mixture. Drop by rounded spoonfuls onto waxed paper.
Bake for 8 to 10 minutes in the preheated oven, or until a toothpick inserted into the center of the cookie comes out clean. Allow cookies to cool completely before cutting into squares.