-
Preheat oven to 350ºF.
-
Bring lemon juice to a simmer in a saucepan over medium heat; cook until reduced by half.
-
Add in 1/2 cup butter and stir until melted.
-
Sift flour, baking powder and salt together in a bowl.
-
Cream remaining butter and sugar until light and fluffy.
-
Add egg and lemon butter.
-
Mix until pale, about 3 minutes.
-
Mix in vanilla.
-
Add in flour and mix well.
-
Form 1-1/2" balls and drop them onto cookie sheets lined with parchment paper.
-
Bake until lightly browned, 12-15 minutes.
-
Cool on rack and store in airtight container, (if they last that long!).