Step 1

Preheat the oven to 350 degrees.  Cover baking sheets with parchment paper or silicone baking sheets.

Step 2

Whisk flour, baking powder, baking soda, and salt; set aside. Cream butter and sugar together until light and fluffy, using a stand or hand mixer on medium. Turn the mixer to low. Add egg, lemon zest, lemon juice, and vanilla extract; mix just until incorporated.

Step 3

Add the flour mixture to the butter mixture in three parts. Mix on low just until incorporated. Using  1 1/2 tablespoon cookie scoop, place dough on prepared baking sheets about 2 inches apart. Bake for  10-12 minutes or until very lightly browned on the edges. Cool on cookie cooling racks.

Step 4

In a small bowl, whisk together powdered sugar, lemon juice, milk, and lemon zest.  Ice fully cooled cookies and place them on cookie cooling racks to set.