Combine all ingredients in a stand mixer until the dough comes together.
Press the dough into an ungreased 9.5-inch tart pan (I used one with a removable bottom to make it easier to remove the shortbread).
Using a fork, poke holes all over the top of the dough.
Put in the oven and bake at 325 degrees for 25-30 minutes or until edges are browned and the center is puffing a bit.
While the shortbread is baking, mix the powdered sugar and enough lemon juice to make a pourable icing.
Set aside the icing until the shortbread is done.
After the shortbread has cooled for a bit, pour the icing over it while it is still warm.
Let it sit for a bit to set and then serve.