Heat the oven to 375 degrees. In a large bowl, beat 1/2 cup sour cream, butter, 1 cup powdered sugar, lemon zest and vanilla on medium speed until blended.
Stir in the flour. Shape the dough into 1-inch balls. Place 2-inches apart on ungreased baking sheet.
Bake for 9 to 11 minutes or until the bottoms begin to brown and the cookies are set. Let cool on the cookie sheet for 1 minute. Remove the cookies to a cooling rack. Cool completely (about 30 minutes).
In a small bowl, beat the remaining 2 tablespoons sour cream, the lemon juice and enough of the remaining powdered sugar until thin enough to coat the cookies. Dip the tops of the cookies in the glaze and shake off the excess. Then dip the glazed tops in the coconut.
Let stand for 30 minutes or until the glaze stiffens.