In a large bowl or the bowl of a stand mixer, beat together the butter, sugar and lemon zest until light and fluffy. Add the eggs one at a time, followed by the vanilla, and mix well. Add the flour, baking powder, and salt, and mix until a firm dough forms.
Form into 2 logs and wrap in plastic wrap and chill at least one hour or up to 3 days.
Preheat the oven to 350℉. Slice the dough into ⅓-1/2 inch thick slices. Place at least on non-stick cookie sheet.
Bake 8-10 minutes or until the bottom edges are just slightly golden. Bake one sheet at a time to ensure even cooking. Do not let tops or sides brown.
Let cool on pan 5 minutes then transfer to rack to cool completely.
Mix together frosting until creamy and spread on cookies. Add sprinkles if desired.
Recipe by Chateau Elma at https://www.chateauelma.com/frosted-sugar-cookies