Be sure the butter is completely softened and room temperature.
Preheat oven to 375 degrees.
Cream together butter and sugar until light and fluffy.
Add the egg and mix until completely combined.
Sift together the flour and baking powder. Add to the creamed butter/sugar/egg in spoonfuls until completely incorporated.
Cover and chill for at least one hour. Roll into small balls. Using a 1 inch cookie scoop makes it easy to keep the cookies uniform in size. Roll in plain sugar or brightly colored decorating sugar.
Place onto cookie sheet. Using the back of a spoon, press down to slightly flatten. Bake for 8-10 minutes or until golden brown.
Notes
*I have made the batter the night before. If you do so, cover tightly and refrigerate. This also makes a great dough if you want to roll out the dough and use a cookie cutter instead!