For the cookies, preheat the oven to 350 degrees Fahrenheit. In the bowl of an electric mixer, cream together butter, sugar, egg, lemon juice and lemon rind. Add flour, baking soda, cream of tartar and salt to the bowl and mix until incorporated.

Scoop dough into 1 1/2" balls and place at least 2" apart on a greased or non-stick baking mat-lined cookie sheet. Press dough balls gently down with the palm of your hand to flatten slightly.

Bake for approximately 8 to 9 minutes. Let cool for a few minutes on the cookie sheet before removing to a cooling rack to cool completely.

For the frosting, in the bowl of an electric mixer, cream together butter, powdered sugar and fresh lemon juice. Add milk, one tablespoon at a time, as necessary, for thinning, mixing well in between, until desired consistency is reached. One Tablespoon was all it took for me. Frost, sprinkle with yellow sugar crystals (optional) and serve.