Cream butter and sugar in a stand mixer until light yellow. Add lime zest, juice and vanilla, mix on low until combined. Add salt, flour and corn starch, mix on medium until dough is smooth.
Place dough on a lightly floured surface. Divide in half and roll each half into a log (about 2" in diameter). Wrap log in plastic wrap in place in fridge for at least 2 hours.
Preheat oven 350 degrees, line a baking sheet with parchment paper. Remove logs from fridge and plastic wrap. Cut into ⅓" slices and place on sheet (they do not spread much so you can place them close but not touching).
Bake for 10 minutes or until the bottoms begin to become golden. Remove from oven and allow to cool on sheet for 5 minutes or until cookie can be handled enough to toss but not yet completely cool. Gently toss with powdered and then allow to cool completely on a wire rack.
Recipe by pretty plain janes at https://prettyplainjanes.com/2016/03/30/lime-shortbread-cookies/