In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and sugar until light and fluffy, about 2 minutes. Add in the egg and the sour cream and mix until combined, about 1 more minute. Add the flour, salt, baking powder and baking soda and mix just until combined. They dough will be wet – not like typical cookie dough.
Using a 1- to 2-tablespoon cookie scoop, scoop the dough onto greased or line baking sheets.
Bake the cookies in the preheated oven until brown around the edges, 7-9 minutes for smaller cookies or 9-11 minutes for larger cookies. Let the cookies cool completely on the baking sheet before removing.
Once the cookies are cool, combine the powdered sugar and sour cream. Dip the tops of the cookies in the glaze, or spread the glaze on top of the cooled cookies.