Dough: In a large bowl cream the butter and both sugars with an electric mixer until fluffy. Beat in the egg, vanilla, lemon juice and lemon zest.
Add in the flour, baking powder and salt. Mix until just combined, the dough will be very crumbly.
Portion and Roll: Divide the dough into 6 equal portions. Form each portion into a ball, pressing just until the dough comes together. Refrigerate for at least 30 minutes.
Bake: Preheat the oven to 350 degrees F while the dough balls are chilling.
Once the dough has chilled, place them in the oven and bake for 15-18 minutes. The edges should look golden brown when finished. Cool 5 minutes and then transfer to a rack to cool completely.
Lemon Frosting: Whip the butter in a large mixing bowl or in the bowl of a stand mixer, until fluffy. Add in the powdered sugar (one cup at a time) and beat to combine. Add up to 5 cups until you've reached the desired frosting consistency. Add in 1 tablespoon of lemon juice and the vanilla extract, continue to mix until combined.
Divide the buttercream into 3 or 4 bowls and add food coloring to each one. Blend until you have achieved the colors you want.
Assemble Frosting Bag: Unroll a large piece of plastic wrap (about 18" long), spread each color of frosting in a line down the plastic wrap, leaving 3-4" on each end. You'll end up with 3-4 horizontal lines of frosting. It's OK if they touch, just don't put them one on top of the other.
Grasp the top and bottom of the horizontal edges of plastic wrap and roll them to close. Frosting will be rolled together now and that's ok! Twist both edge pieces of plastic wrap together, so that you create a tootsie-roll like package of frosting.
Insert the roll of frosting down into your piping bag. Pull it all the way down so that one end of your frosting roll meets the bottom, at the piping tip, and the other end extends out the back of the piping bag.
Snip the plastic wrap off the roll where it meets the frosting tip. Press the frosting down into the tip and pipe frosting on cookies. Top with Easter colored sprinkles. Serve & enjoy!
Decorate cookies: Snip the plastic wrap off where it meets the frosting tip. Press the frosting down into the tip and pipe the frosting onto your cookies. Top each cookie with some Easter-colored sprinkles. Serve and enjoy!