Preheat oven to 350º Line heavy baking sheets with parchment paper.

Beat butter in bowl of stand mixer for a minute or so - scrape down the sides of bowl

Beat in the sugars, and cream together until the mixture is fluffy.

Beat in the egg until creamy and light

Beat in the lime zest.

Add the dry ingredients, and beat until completely incorporated

Form into balls with a medium cookie scoop [1 & 1/2 tablespoon size balls]

Roll balls lightly until smooth, and dip the tops into the sanding sugar.

Place sugar side up on prepared pan and bake for 12 minutes - there will only be a slight browning at the edges, but cookies should be firm to the touch.

Cool on a rack. Will keep at room temperature in a sealed container for a week.