Step 1 – Prep & Wet Mix:
Preheat oven to 350°F (175°C). Line cookie sheets with parchment paper.
In a large bowl, beat butter and sugar until light and fluffy (2–3 minutes).
Mix in egg until well combined.
Add lemon zest, lemon juice, and vanilla. Mix (it's okay if it looks curdled).
Step 2 – Dry Ingredients:
In a separate bowl, whisk together flour, baking powder, and salt.
Gradually add dry ingredients to the wet mix. Mix until just combined.
Dough should be soft but hold together. If sticky, chill for 30 minutes.
Step 3 – Shape & Bake:
Scoop 1.5" balls (about 2 tbsp dough).
Roll in sugar (optional) and place 2 inches apart on baking sheets.
Flatten slightly and bake for 10–12 minutes.
Let cool 5 minutes on sheet, then transfer to rack.
Step 4 – Make Glaze:
Whisk powdered sugar, lemon juice, and zest.
Add milk 1 tsp at a time until pourable.
Step 5 – Glaze:
Once cookies are cool, spoon or drizzle glaze over top.
Let set for at least 1 hour before stacking/storing.