Add the egg, key lime juice, and key lime zest. Beat until combined, scraping down the sides of the bowl as needed.

In a separate bowl, mix the flour, salt, and baking powder. Add into the main bowl, 1 cup at a time, mixing until just combined. Mix in white chocolate.

Shape and roll the dough until it is ¼ inch thick. Chill for 30 minutes.

Using any desired cookie cutter, cut the cookies and place them on a lined baking tray. Chill the dough again while preheating the oven to 350° Fahrenheit.

Bake for 7 to 9 minutes or until the edges are lightly browned.