- With the rack in the middle position, preheat the oven to 375°F (190°C). Line two baking sheets with silicone mats or parchment paper.
- In a bowl, combine the flour and baking powder.
- In a large bowl, cream the butter, sugar and zest with an electric mixer. Add the egg and beat until smooth. Stir in the dry ingredients alternately with the lemon juice.
- Shape the dough into balls, using about 1 tbsp of dough for each cookie. Space them evenly on the prepared sheets.
- Bake for 10 to 12 minutes or until the cookie edges just begin to brown. Let cool completely on the baking sheets. The lemon cookies will keep for 2 weeks in an airtight container at room temperature.