Preheat oven to 350 degrees F. Cookies: In a large mixing bowl, blend all ingredients together and chill for up to 1 hour. Roll dough out on floured board about 1/8-inch thick. Cut desired shapes with cookie cutters and place onto sheet pan. Bake for 8 minutes in preheated oven. Let cool to room temperature before decorating.
For Royal Icing: With a hand mixer, beat the egg whites with the lemon juice or extract until frothy. Add the sifted powdered sugar and beat on low speed until combined, smooth, and shiny. Turn to high and beat approximately 5 minutes until stiff and glossy. Transfer to a pasty bag or zip top bag to pipe onto cookies. Decorate, if desired.