Preheat oven to 375°F.

Let butter soften in large bowl. Add sugar, egg, vanilla and lemon zest and then blend everything together in bowl. Add sour cream. In another bowl, sift together flour, soda and salt. Add to butter mixture and blend. Using a rolling pin, roll out dough on lightly floured surface to 1/4" thickness. Cut out cookies with cookie cutter. Place on greased baking sheet and bake at 375 20- 22 minutes or until lightly browned. Frost and decorate.

For icing: Mix all ingredients together with hand mixer on medium speed, adding powdered sugar if needed. Spread or pipe frosting onto cookies. Add food coloring if desired.