In a large mixing bowl, cream the butter and cream cheese together until soft and creamy.
Blend in the sugar and acesulfame-K.
Blend in the egg.
In another bowl, sift together the flour and baking powder.
In a small bowl mix together the butter extract and sour cream.
In the large mixing bow containing the butter and cream cheese, alternately add the flour mixture and the sour cream mixture.
Blend thoroughly.
Make a ball and wrap it in plastic wrap.
Refrigerate until chilled.
Roll dough on a lightly floured board until it is about 1/8 in. (3 mm) thick.
Use cookie cutters to cut the dough into shapes.
Place cookies on a baking sheet that has been coated with non-stick cooking spray.
Bake in a preheated 400°F (200°C) oven for 8-10 minutes.