Using an electric mixer on high speed, whip the egg whites until they hold soft peaks. Continue whipping and gradually add the remaining confectioners' sugar, mixing for about 2 more minutes. The whites should be thick, creamy, and somewhat stiff. Set aside 2/3 cup of the egg white mixture for tops of cookies.

Gently fold the ground almond mixture and lemon zest into the egg whites mixture. The dough will be stiff.

Lay a sheet of parchment paper or waxed paper on a clean, flat work surface. Place the dough on the paper. Flatten the dough and lightly dust with confectioners' sugar. Cover the dough with another sheet of paper.

Roll the dough between the  papers to a 1/4-inch thickness. Carefully flip the dough over. Gently peel off the top sheet of paper. Lay the paper back onto the dough and flip again. Peel the other sheet of paper so that the dough is not stuck to either sheet of paper.

Using a 3-inch star-shaped cookie cutter, cut out the cookies and place them about 2 inches apart on the prepared baking sheets. Gather and re-roll the dough as needed.

Use an offset spatula or small spoon to spread the remaining meringue mixture on top of each cookie. Do not let the meringue drip over the sides. Place the remaining almonds on top of meringue in whatever pattern you like.

Bake 30 minutes, or until the bottoms of the cookies are light golden brown and the meringue is set and crisp. Turn off the oven and open the oven door. Leave the cookies in the oven for 10 minutes to allow them to dry.