Line baking trays with parchment paper or silicone baking mats. Preheat oven to 325 degrees Fahrenheit.
Beat egg in a small bowl. Set aside.
Cream butter and sugar in a large bowl until light and fluffy. Beat in all but 1 Tbsp of the beaten egg. Set the saved portion aside. Add the almond extract to the butter mixture. Mix to combine.
Combine the flour, baking soda and salt in a separate bowl. Add to butter mixture and mix to combine.
Scoop the cookie dough and round into balls (about 1½ Tbsp each). Place on prepared baking sheets, 2-inches apart. Flatten to ½-inch thick with the bottom of a drinking glass.
Gently press a single almond halfway into the center of each cookie dough ball. Add ½ tsp water to the saved beaten egg and whisk together. Brush the tops of the cookies with the egg mixture.
Bake 14 to 16 minutes or until lightly golden brown. Cool for 2 minutes before transferring to a wire rack to cool completely. Store leftovers in an airtight container up to 5 days.