How to Make It
Heat oven to 375° F. Line a large baking sheet with parchment paper.
In a large bowl, beat the butter, granulated sugar, lemon zest, and salt with an electric mixer on medium speed until creamy. Beat in the egg yolk and extracts until well incorporated. Reduce the speed to low, gradually add the flour and beat just until clumps form.
Scatter the clumps evenly on the prepared pan. Press them into a rough rectangle, then roll neatly into a ¼-inch thick 10- by 16-inch rectangle. In a medium bowl, whisk the egg white until frothy and fold in the almonds and confectioners' sugar. Spread the egg mixture onto the dough in an even layer and gently press it down. Cut the dough crosswise into 2-inch strips, then cut again on a diagonal in 1-inch strips. Dust with confectioners' sugar.
Bake until golden brown, 20 to 25 minutes. Cool completely in the pan on a wire rack. Carefully break the cookies along the cuts.
Storage tip: The cookies will keep in an airtight container at room temperature for up to 2 days or in the freezer for up to 1 month.
Tips: A ruler and a pizza wheel make cutting easy. And while this diamond shape is pretty, you can cut these cookies any way you like.