1. In a mixing bowl, cream together softened butter, sugar, vanilla, lemon flavoring, and egg until light and fluffy. Add yellow food coloring gel.

2. Mix flour and baking powder in a separate bowl. Gradually add this dry mixture to the wet ingredients to form the cookie dough. Roll into balls and bake at 350°F for 15 minutes.

3. While cookies cool, mix softened butter, cream cheese, and powdered sugar to make the frosting. Divide into two bowls and color one yellow and the other blue.

4. Pipe the frosting onto cooled cookies in a swirl pattern and top with a blueberry. Allow frosting to set before serving.