Note: You will need to chill the dough for at least two hours, so plan accordingly.
In a large bowl, beat butter until light and fluffy. Add sugar and beat until well combined. Add egg; mix until well combined. Stir in buttermilk, lemon peel, lemon juice and vanilla. In a separate small bowl, sift together flour, baking soda, and salt. Gradually add to the butter mixture.
Preheat the oven to 350 degrees. Drop small rounded teaspoons of dough onto parchment lined or lightly greased cookie sheets. Bake for 6-8 minutes or until the edges are slightly golden. Sprinkle a pinch of sugar over each cookie. Remove to wire racks to cool.
Optional: Glaze the cookies once they have cooled.