Combine all-purpose flour, baking powder, and salt in a small mixing bowl and set aside.
With an electric mixer, cream the butter and sugar together until light and fluffy.
Beat in egg, ricotta, lemon juice, and lemon zest.
Stir in the all-purpose flour, baking powder, and salt.
Cover and chill in the refrigerator for one hour or overnight. (Do not skip this step!)
Preheat oven to 350 degrees. Line a baking pan with parchment paper.
When the dough is chilled, remove it from the refrigerator and drop by tablespoon onto a parchment-lined baking sheet, leaving 2 inches of space between each cookie to allow for spreading.
Bake in preheated oven for 12 minutes, until set, and just beginning to show some brown.
Remove the from oven and transfer to a wire rack to cool.
While the cookies cool, make the icing. Stir powdered sugar and lemon juice together in a small bowl, adding just enough lemon juice to form a drizzle.
Drizzle over cookies, and top with additional lemon zest, or sprinkles as desired.