In a large bowl whisk together the flour, baking powder and salt. Set aside.
In the stand up mixer or large bowl, beat the butter and sugar until light and fluffy 3-4 minutes. Then add the egg and beat together (speed 2), while still beating add the discard, ricotta, zest and vanilla and combine.
On low speed add the flour mixture and beat just until combined. Scrape the bowl down, make sure there is no flour under the batter that hasn't been mixed in. Cover with plastic wrap and refrigerate for 1 hour.
Pre-heat the oven to 350F (180C). Line 1-2 cookie sheets with parchment paper.
Remove the dough from the fridge and drop by spoonfuls on the prepared cookie sheets, bake for 15-17 minutes until lightly golden. Let cool for about 3-5 minutes on the cookie sheets then move to a wire rack. Drizzle the cookies with the glaze when completely cool if desired. Or dust with powdered sugar.
LEMON GLAZE
In a medium bowl whisk together the icing sugar, juice and zest. If too thick add more lemon juice or milk, if too think add more powdered sugar.