Grind almonds in a food processor or blender.
Combine powdered sugar and almonds in a small bowl. Set aside.
Place butter in large mixer bowl. Beat at medium speed until creamy (1 to 2 minutes). Add sugar-almond mixture to butter; beat until well mixed (1 minutes). Add egg yolks and lemon peel; beat until well mixed (1 to 2 minutes). Reduce speed to low. Add flour and salt; beat until well mixed (1 to 2 minutes). Cover; refrigerate until slightly firm (30 minutes).
Heat oven to 350 degrees F. Roll dough into one inch balls. Place 2 inches apart onto ungreased cookie sheets. Flatten with bottom of glass. Sprinkle with decorator sugar, if desired. Bake for 9 to 11 minutes or until edges are browned.