Preheat the oven to 350°F or 175°C and line baking sheets with parchment paper.
Whisk the flour, baking soda, and salt together in a bowl and set aside.
Beat the butter and sugar until light and fluffy, about 2 to 3 minutes.
Mix in the egg, lemon juice, lemon zest, and vanilla until smooth.
Gradually add the dry ingredients, mixing just until combined and adjusting with a little flour if sticky.
Roll the dough into 1 inch balls, coat in sugar, and space them 2 inches apart on the sheets.
Bake for 8 to 10 minutes until edges are set and centers stay soft.
Cool briefly on the pan, then transfer to a rack to cool completely.