
In a large bowl using a handheld mixer (or in the bowl of a stand mixer with the whisk attachment), whisk the egg whites on medium speed for 1 to 2 minutes until soft peaks form. While mixing on medium-low speed, gradually add 1¼ cups (150g) of powdered sugar.
Once all of the sugar is added, scrape down the sides of the bowl and increase the speed to medium-high. Beat for 2 to 3 minutes until the mixture is thick, glossy and leaves a trail that holds its shape on the surface of the mixture for a few seconds when drizzled. Set aside ½ cup of this egg-white mixture in another small bowl (this will be used to ice the cookies later).
In another medium bowl, mix to combine the remaining ½ cup (60g) powdered sugar, ground almonds, cinnamon, lemon zest and salt. Sprinkle this mixture over the large bowl of egg white mixture and add the lemon juice. Fold to combine.
Scrape down the sides of the bowl with a silicone spatula or bowl scraper and knead with your hands to create a ball of dough. (If the dough is sticking to your hands or the bowl, lightly sprinkle with powdered sugar so that you can knead it into a cohesive ball.) Cover and refrigerate for 20 minutes.
Preheat the oven to 250°F. Line 2 large baking sheets with parchment paper.
Generously sprinkle a surface with powdered sugar. Pat the cookie dough into a flat rectangular shape, then lightly sprinkle the top of the dough with more powdered sugar. Using a rolling pin, roll the dough to be ¼-inch thick.
Cut cookies using a 2½-inch to 3-inch wide star-shaped cutter, dipping the cutter in powdered sugar between each cut. Place them on the prepared baking sheets leaving about 1-inch of space between each. Knead together any dough scraps, re-roll and cut. (You can continue to do this until all of the dough is used.)
Dollop ½ to 1 teaspoon of the reserved egg white mixture onto the center of each cookie. Use a very small pastry brush or toothpick to spread the mixture and cover the points of the stars.
Bake one sheet tray at a time for 25 to 30 minutes or until the bottoms just start to turn golden brown and the meringue is dry but not turning brown. Turn off the oven and leave the oven door open about 6 inches for another 10 minutes. Remove the cookies from the oven and transfer them to a wire rack to cool completely. Repeat with the other baking sheet.