Preheat the oven to 350 degrees. Line a baking sheet with parchment paper or a baking mat.
Sift together the flour, baking powder, and salt. Set this aside
In a large bowl add the sugar and orange zest. With your fingers rub the zest and the sugar together until the zest is mix throughout the sugar.
Add the butter to the sugar mixer. With an electric mixer mix until well blended.
Add the egg and the orange juice and mix in.
Slowly add the dry ingredients, mixing after each addition until just incorporated.
Drop cookies from rounded full teaspoon onto the prepared baking sheet.
Bake for 10 to 12 minutes or until the edge of the cookies are golden brown.
Cool on a cooling rack until completely cooled.
Make the frosting while the cookies are cooling.
To make the frosting, combine the powdered sugar, 2 tablespoons soft butter, and a dash of salt. Slowly add the orange juice until the right consistency for frosting. Beat until smooth.
Frost cooled cookies.