Preheat ovenoven to 400°F. Line baking sheets with parchment paper. Set aside.

In a small bowl, combine sugar and lemon zest. Mix with fingertips until sugar becomes moist and fragrant.

In a medium bowl, combineflour and baking powder.

In a large bowl, with an electric mixer, beat butter until creamy. Add lemon sugar and 1 package of gelatin; beat until light and fluffy, about 3 minutes.

Add in egg and vanilla and mix to combine.

Gradually beat in flour mixture until thoroughly combined.

Shape dough into 1-inch balls. Place, 2 inches apart, on prepared baking sheets. Flatten dough balls with the bottom of glass. Sprinkle tops of cookies with remaining dry gelatin mix.

Bake cookies in preheated oven for 8 to 10 minutes or until edges are lightly browned. Cool on baking sheets for 3 minutes before removing to a wire rack to cool completely.

Cookies can be stored in an airtight container at room temperature for up to 3 days.