Stir together flour, powder & salt in med bowl. Beat butter, sugar, egg & vanilla in bowl until well blended. Stir in flour mixture. Gather dough together & shape into ball, wrap & refrigerate several hours or overnight. Preheat oven to 350ºF.  Lightly coat baking sheets with nonstick spray. Roll out dough with lightly floured rolling pin on lightly floured surface to 3/8" thickness. Cut into cookies with 2 1/2" holiday shaped cookie cutters. Place cookies on prepared cookie sheets, spacing 1 1/2" apart. Decorate with colored sprinkles, sugars & gum drops if you wish. Bake in oven 10-12 minutes or until lightly browned around edges. Remove to wire racks to cool.