Prep your tools. Line two baking sheets with parchment paper. Set the oven to 350°F (175°C) so it heats evenly while you mix.

Cream the butter and sugar. In a large bowl, beat the softened butter with the granulated sugar until light and fluffy, about 2–3 minutes. Look for a pale color and creamy texture.

Add wet flavor boosters. Beat in the egg, lemon zest, lemon juice, and vanilla. The mixture may look slightly curdled from the citrus. That’s normal and will smooth out once the flour goes in.

Whisk the dry ingredients. In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. This ensures even distribution and prevents clumps.

Bring the dough together. Add the dry ingredients to the wet mixture and mix on low until just combined. Stop as soon as no streaks of flour remain. Overmixing can make the cookies tough.

Chill the dough. Cover the bowl and chill for 20–30 minutes. This helps the dough firm up so the cookies don’t spread too much.

Shape and sugar. Scoop tablespoon-size portions and roll into balls. Roll each ball lightly in granulated sugar for a crisp finish, then place on the prepared sheets, leaving a couple inches between cookies.

Bake. Bake for 9–11 minutes, until the edges are set and just turning lightly golden. The centers should look slightly soft; they’ll continue to set as they cool.

Cool. Let the cookies rest on the baking sheet for 5 minutes, then move them to a wire rack to cool completely.

Optional glaze. Whisk the powdered sugar with lemon juice until smooth and drizzle over cooled cookies. Let the glaze firm up before serving.