Key Lime Sugar Cookies

Preheat oven to 350ºF.

In the bowl of a mixer, cream together butter, sour cream and sugar. Beat in eggs. Add vanilla, key lime juice and zest. In a bowl, combine flour, baking soda, salt and cream of tartar. Carefully add dry ingredients to batter. Beat until combined.

Using a cookie scoop, scoop out dough about the size of a walnut, and with floured hands, roll into a ball. Place on cookie sheet. Flatten cookies with the bottoms of a glass that has been dipped into sugar.

Bake for 10 minutes. Do not over-bake. Let cookies rest on baking sheet for 2 minutes before removing to a cooling rack.

For the frosting, cream together butter and shortening. Add powdered sugar 1 cup at a time. Blend in key lime juice, zest, and salt. If frosting is too thick, add milk or water until creamy. Frost over completely cooled cookies.