Preheat the oven to 350 degrees F (180 degrees C).
Line your cookie sheets with parchment paper or silpats.
Using a mixer, mix the softened Unsalted Butter (1 cup) and Granulated Sugar (1 1/2 cup) until combined. Add the whole Egg (1) and mix.
Add the Sunkist Orange (1 teaspoon) and Vanilla Extract (2 teaspoon), then mix well.
In a separate bowl, mix the All-Purpose Flour (1 3/4 cup) with the Baking Powder (2 teaspoon) and Salt (1 teaspoon). Add it to the butter, and mix together. Do not overbeat.
Use your hands to press the dough together, and form two balls of dough. Sprinkle some flour on a clean counter, and roll out your dough. Cut the dough into your preferred shapes using a cookie cutter. Reuse the scraps as you go.
Carefully transfer cut out cookies to the cookie sheets. Bake 8-9 minutes, or until the edges are lightly browned.
Remove from the oven, and cool on the sheets for 5 minutes. Transfer to a cooling rack, and let cool completely before icing.
For the icing, place the Egg (2) into a bowl, and add the Lemon Juice (to taste) and Salt (1 pinch). Whisk together with a mixer to loosen the egg whites. Start beating them until they are frothy.
Add Powdered Confectioners Sugar (3 cup), half a cup at a time, beating well after each addition, until you have reached the desired consistency.
Decorate cookies with the icing. Keep a damp paper towel over the icing as you work, or it will dry up. Sprinkle them as you wish with Green and Red Colored Sugar (to taste).