¾cup(170g)salted butter, softened to cool room temperature
½tablespoonfresh lemon zest, (optional; but delicious)
2 ¼cups(320g)all-purpose flour
6tablespoonssalted butter, softened
2 ½cups(285g)powdered sugar
3tablespoonsmilk or cream
Preheat oven to 375 degrees F.
For the bars, in a large bowl, cream together the butter, granulated sugar and powdered sugar until light and fluffy. Add the eggs and vanilla and mix for 1-2 minutes. Stir in the lemon zest (optional), flour, baking powder and salt. Mix until combined.
Lightly grease a 9X13-inch baking pan with cooking spray or line with parchment paper and grease. Press the sugar cookie dough into an even layer in the bottom of the pan.
Bake for 10-13 minutes. Don't overbake! The bars should have hardly any color around the edges and barely be set in the middle. Let the bars cool completely before frosting.
For the frosting, cream together the butter and powdered sugar until smooth (if the mixture has trouble coming together, add a drop or two of milk). Add in the vanilla, milk or cream, and food coloring (if using), and mix until the frosting is light and fluffy, 1-2 minutes.
Spread the frosting over the cooled bars and top with sprinkles.