Preheat oven to 375. Melt buttter set aside to cool. Place powered sugar and cornstarch in shallow dish and mix with fork to blend.
Put cake mix cooled butter, eggs and lemon zest into large mixing bowl. Mix by hand until well blended and a dough forms. If necessary add a little flour to dough if its sticky. Use littel flour at a time util the dough forms into 1-inch balls and roll in powered sugar. Place on cool ungreased baking sheets about 2 inches apart.
Bake one sheet at a time in center of oven for 9 to 11 minutes or until set. Cool 1 minute then transfer the cookies on wax paper instead of racks and did not have any issues while and after they cooled. Store in airtight container separate layers if needed with parchment or wax paper.
I used a small cookie scoop about an 1 inch to keep the cookies consistent in size. Then rolled them in my hand to make a ball and rolled them in the powered sugar to coat evenly.