• Preheat the oven to 350 degrees Fahrenheit and line 2-3 baking sheets with parchment paper.
• In a medium bowl, whisk together the 2 cups all-purpose flour, ½ teaspoon salt, and ½ teaspoon baking powder. Set aside.
• In another medium bowl, whisk together the ½ cup softened unsalted butter and ⅔ cup granulated sugar for 2-3 minutes until light and fluffy. Add the 2 egg yolks, 2 tablespoons sour cream, 1 ½ tablespoons vanilla extract, and 1 teaspoon lemon extract and mix until just combined.
• Add the flour mixture to the butter mixture and mix until just barely combined.
• Split the dough into 2-3 pieces and roll them one at a time on a lightly floured surface until they are ¼ inch thick. Use a Christmas tree cookie cutter (or alternative shapes!) to cut out the cookies.
• Press the scraps together and set them aside to rest for about 5 minutes. Then re-roll the scraps and cut more cookies until all the dough has been used.
• Place the cookies on the parchment-lined cookie sheets, leaving 1 ½ inches between them.
• Bake the cookies for 7-8 minutes, rotating the pan in the oven after 4 minutes to ensure they bake evenly. The edges will be just set and the cookies will be very light in color and should have very minimal coloring underneath them.
• Let the cookies cool on the pan for 2 minutes for the shape to set before transferring to a cooling rack. Let the cookies cool completely before frosting.

Royal Icing

• Whisk 4 cups sifted powdered sugar with 3 tablespoons meringue powder in a large bowl or the bowl of a stand mixer before adding 1 tablespoon light corn syrup, ½ teaspoon clear vanilla extract if desired, and about 6 or 7 tablespoons of the 8-12 tablespoons water. Slowly mix with the paddle attachment or a hand mixer until the sugar is moistened, then beat on medium-high speed for 2-3 minutes. It should be quite thick at this stage.
• If you would like to use some of the icing to pipe more defined details that will hold their shape, reserve some of the icing in a separate bowl and cover tightly with plastic wrap.
• For smooth designs, add additional water to the icing 1 or 2 teaspoons at a time until the icing drips back into the bowl and the lines of icing take about 10 seconds to melt back into the rest when the whisk is lifted out of the bowl. If it melts back in too quickly, add a tablespoon or two of powdered sugar to thicken it up again.
• Color the different bowls of frosting using your choice of gel food coloring. Use piping bags or dip the completely cooled cookies as desired, keeping the icing covered tightly between using colors, as it will dry and crust over quickly. Let the icing set up for several hours before stacking them gently.