Preheat the oven to 350ºF. Line 2 baking sheet pans with parchment paper.
In a separate bowl, combine flour, baking powder, and salt, then mix until well combined. Set aside.
Add the butter, granulated sugar, and powdered sugar to the mixing bowl. Turn your mixer to low speed, and mix until incorporated. Turn the mixer to medium-high speed and mix until creamy and fluffy. Stop the mixer to scrape the sides of the bowl.
Add the egg yolks one at a time. Continue mixing and add lemon juice, lemon zest, and vanilla. Mix until they're all incorporated and light in color.
Turn the mixer to low and slowly add the flour mixture. Turn the speed to medium-high, mix the dough until well combined, and until it turns to a thicker consistency.
Fit large star tip to the piping bag. Fold the bag under your hand and hold it. Fill the bag half-way with the cookie batter. Squeeze the bag, pipe rosettes onto the prepared baking pan.
Bake for 10-15 minutes or until the edges turn golden brown.