Preheat oven to 350F degrees. Line a baking sheet with parchment paper or a silicone baking liner.
Prepare Ingredients
Using a fine-edged grater, zest one large lemon to make 1 tablespoon zest.
Make the Dough
In a medium-sized bowl, cream together the softened butter and granulated sugar until creamy. Beat in lemon zest, lemon juice, vanilla extract, and large eggs.
In a small bowl, combine the all-purpose flour, baking powder, and salt.
Gradually stir flour into the creamed mixture. Dough will be sticky.
Prepare the Biscotti
Scoop the dough onto the prepared baking sheet and pat it into a flattened log about 13 inches long, 3 inches wide, and about 3/4" thick. Smooth out the top and sides using a wet spatula. Bake in preheated oven for 25 minutes.
Remove from oven. Spray with water, spritzing the sides and top. (This will soften the crust just enough to make slicing easier.) Reduce oven temperature to 325 degrees.
Wait five minutes, then cut crosswise with a sharp knife into 1/2" slices. Place the cookie slices on the baking sheet standing up on edge.
Bake for another 30-35 minutes, until biscotti feel very dry and are golden around the edges. Remove from oven and transfer to a rack to cool.
Once they have cooled, drizzle with glaze.
Make the Lemon Glaze
To make glaze, in a small bowl, combine the powdered sugar, lemon juice, and whole milk. Whisk together until smooth.
Drizzle over the cooled biscotti. Allow to set completely before storing. May store biscotti in a tightly covered container for 4-6 weeks in a cool, dry place. Makes 2 dozen.
Notes
*Unless otherwise indicated, all butter used on this recipe site is salted.