Decorate the green trees with dough from the white trees and the white trees with dough from the green trees. Whichever trees, your guests sample, the lemon flavor of these Christmas cookies will be a pleasant surprise.
1. In medium bowl, whisk flour, baking powder, salt. In large bowl, beat butter and sugar until smooth, 1 minute. Beat in egg, vanilla, rind, juice. On low, beat in flour mixture. Remove half of dough to bowl; tint green. Flatten each half of dough into 8-inch disk; wrap each in plastic. Chill 2 hours.
2. Heat oven to 350 degrees F. On floured surface, roll out green dough, 1/8 inch thick. Cut out trees with 3-inch tree cookie cutter. Place on ungreased baking sheets. Gather scraps; reroll; cut out more trees. Repeat with white dough. Chill 10 minutes. Using 1/2-inch-round aspic cutter and flouring edge frequently, cut rounds from trees; put green circles in cutouts in white trees, and white circles in green trees.
3. Bake in 350 degree F oven until golden around edges, 10 minutes.Glaze:
4. Mix sugar and juice. Brush on hot cookies; cool.